BULLETIN

OF THE

UNITED STATES

GEOLOGICAL SURVEY

No. 94=

UNITED STATES GEOLOGICAL SURVEY

J. W. POWELL, DIRECTOR

THE

MECHANISM OF SOLID VISCOSITY

BY

CARL BA.RUS

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1892

CONTENTS.

Pago.

Letter of transrnittal ....................................................... 13

Preface........................-......-.............--.----.-.......-.------ 15

CHAPTER I. Tensile, drawn, and other strains in their bearing on Maxwell's

theory of viscosity.................................................. 17

Introductory ........................................................... 17

Apparatus........................ ... - ---- --- -- - --- 18

Data for drawn wires ...................................,......... ..'.... 18

Data for stretched wires ................................................ 24

Inferences ............................................................... 26

CHAPTER II. The two species of molecular break-up which promote viscoiia

deformation ........................................................ 30

Introductory............................................................ 30

Motional annealing denned.............................................. 30

Strain, electric resistance, and viscosity ................................. 31

Temper, electric resistance, and viscosity................................ 31

Data relative to temper, electric resistance, and viscosity................ 31

Discussion of results .................................................... 33

Data for cyclic twisting.................................................. 33

Discussion of results of cyclic twisting .................................. 37

The marked feature ................................................. 37

Analogy with thermal annealing .................................... 38

CHAPTER III. The effect of mechanical strain on the carburation of steel.... 40

Introductory ........................................................... 40

Drowne's experiments............................................... 40

The present method................................................. 40

Method of experiment................................................... 41

Results obtained................................... ..................... 41

Tables.................................................................. 42

Discussion........................................ ...................... 44

Inconsistency of the results ........................... ....... .r ...... 44

Errors of the method............. ................................... 45

Temperature...........'............................................. 45

Concentration of acid................................................ 45

Solution in air and in hydrogen ...................................^. 45

Eate of solution .. ^................................................... 46

Structural density ................................................... 46

Summary ............ ......... ........................................ 46

Osmond's a and /? iron ................................ ......... ..... . 47

CHAPTER IV. The effect of strain on the rate of solution of steel............ 48

Introductory ............................................................ 48

Method................................................................. 48

Tables........................................................ 4 ......... 49

6
6 CONTENTS.

Page. 

CHAPTER IV. The effect of strain on the rate of solution of steel Continued.

Discussion.............................................................. 57

Incidental errors.................................................... 57

Effect of surface .................................................... 58

Effect of diffusion................................................... 58

Wires originally soft................................................ 59

Wires annealed ..................................................... 60

Relation to Drowne's inferences..................................... 61

Summaiy..........................................;................ 61

CHAPTER V. The hydroelectric effect of changes of molecular configuration. 63

Introductory ........................................................... 63

Apparatus....".......................................................... 63

Experiments............................................................ 64

Zero method........................................................ 64

Eesults for iron ..................................................... 64

Discussion of results .................................................... 66

Data for divers metals .................................................. 66

. Effects classified ........................................................ 69

Discussion of errors ................................'..................... 70

Variable capacity................................................... 70

Single wires ............................................................ 72

Summary............................................................... 72

CHAPTER VI. Secular annealing of cold hard steel.......................... 74

Introductory............................................................ 74

Results f()r homogeneity of rods ........................................... 75

Mass constants of rods.................................................. 76

Electrical constants of rods ............................................. 77

Summary............................................................... 79

CHAPTER VII. The viscosity of electrolysing glass.........................; 80

Apparatus .............................................................. 80

Results......................-.............".............-..........-.... 81

Inferences.....................................................1........ 82

CHAPTER VIII. The electrical resistance of stressed glass................... 85

Introductory............................................................ 85

Apparatus.............................................................. 85

Experiments............................................................ 86

Data for 350° ....................................................... 86

Data for 100° ....................................................... 86

Data for 185° ....................................................... 88

Results of twisting.................................................. 89

Differential apparatus .............................................. 89

Results for torsion .................................................. 91

Character of traction effects......................................... 91

Results for traction at 190°.......................................... 91

Discussion of these results .......................................... 92

Traction at 100° ..................................................... 94

Further results at 100°.............................................. 95

Dimensional change due to torsion .................................. 96

Effect of temperature ............................................... 96

Traction at 360°..................................................... 97

Summary........................................................... 98

Degree of molecular instability of glass.............................. 99

CHAPTER IX. The energy potentialized in permanent changes of molecular

configuration....................................................... 101

Introductory ........................................................... 101
CONTENTS. 7

Page. 

CHAPTER IX. The energy potentialized in permanent changes of molecular

configuration Continued.

Apparatus ............................................................... 101

Eesults................................................................. 103

Discussion of errors..................................................... 104

Successive stretching ................................................... 105

Eesults of improved methods............................................ 106

Summary............................................................... 107

CHAPTER X. The chemical equilibrium of solids in its relation to pressure

and to temperature ............................................... 109

Earlier researches ...................................................... 109

Apparatus.............................................................. 110

Compressor......................................................... 110

Vapor baths......................................................... 110

Insulation.......................................................... 110

The resistance tube ................................................. Ill

Arrangement for testing insulation.................................. 113

Digression.......................................................... 113

Resistance measurement ............................................ 114

Galvanometer ................. '. .................................... 114

Other adjustments.................................................. 114

Observations ........................................................... 114

Tables explained .................... .............................. 114

Remarks on the table............................................... 115

Electromotive force................................................. 116

Remarks on the table............................................... 116

. Pressure coefficient of sperm oil..................................... 117

Pressure coefficient of gasoline...................................... 117

Pressure coefficient of petroleum .................................... 118

Pressure coefficient of thin machine oil.............................. 120

Pressure coefficient of thick machine oil............................. 122

Digest.............................................................. 123

Deductions............................................................. 124

Effect of pressure. .................................................. 124

Temporary and permanent effects ................................... 124

Chart .............................................................. 125

Pressure and chemical equilibrium.................................. 125

Effect of temperature............................................... 125

Molecular effects of stress........................................... 125

Hysteresis.......................................................... 126

Magnetic hysteresis ................................................ 127

Mechanism of viscosity ......................,........_............. 128

Electrical effects of ceolotropic stress................................ 130

Unavoidable errors ..................................................... 130

Polarization........................................................ 130

Insulators.......................................................... 130

Shifting isothermal planes ................_......................... 130

Electromotive force................................................. 131

Short-circuiting.................................................... 132

Electromotive force and pressure.................................... 132

Graphic representation ..................._......................... 133

Electric instability of hydrocarbon oils .............................. 134

Conclusion ............................................................. 135

Index ................................................................... 137

ILLUSTRATIONS.

Page. 

FIG. 1. Apparatus for comparing viscous deformations...................... 19

2. Time variation of viscous deformation in case of soft steel transformed by temper, drawn strain, traction, and torsion, respectively ........................................................... 28

3. Withdrawn.

4. Apparatus for measuring the hydroelectric effect of stretching...... 64

5. Apparatus for testing the viscosity of electrolyzing glass ........... 81

6. Apparatus for testing the viscosity of electrolyzing. glass ........... 82

7. Apparatus for testing the viscosity 'of stressed glass ................ 86

8. Apparatus for testing the viscosity of stressed glass................ 88

9. Apparatus for testing the viscosity of stressed glass................ 88

10. Apparatus for testing the viscosity of stressed glass 200° ........... 90

11. Apparatus for testing the viscosity of stressed glass 100° ........... 90

12. Apparatus available at 360°........................................ 97

13. Apparatus for measuring the thermal effect of stretching ........... 102

14. Tube for measuring the pressure increments of the electric resistance of glass.................................................... 110

15. Diagram of resistance tube in place ................................ Ill

16. Improved form of resistance tube. ................................. 112

17. Arrangement for measuring the pressure increments of the electric resistance of liquid insulators...................................... 113

18. Pressure coefficient and temperature for sperm oil and for glass..... 117

19. Pressure coefficient and temperature for gasoline ................... 118

20. Pressure coefficient and temperature for petroleum and for glass .... 120

21. Pressure coefficient and temperature for thin mineral machine oil

and for glass .................................................... 122

22. Pressure coefficient and temperature for thick mineral machine oil

and for glass .................................................... 124

23. Diagram .......................................................... 131

24 5 Charts showing the oscillation of the electric conductivity of

( glass and of viscous hydrocarbon oil............................ 133

Q

TABLES.

Tage.

TABLE 1. Viscosity of hard-drawn steel wire compared with soft. .......... 20

2. Viscosity of hard-drawn steel wire compared with soft ........... 21

3. Viscosity of hard-drawn steel wire compared with soft............ 22

4. Viscous eft'ect of moderate traction ............................... 23

5. Digest for hard and soft wires.................................... 23

6. Viscous effect of cyclic traction.................................... 25

7. Viscous effect of motional annealing .............................. 32

8. Electrical effect of motional annealing............................ 33

9. Viscous deformation in case of cyclic twisting..................... 34

10. Graphitic carbon in soft and in drawn steel........................ 42

11. Solution of soft steel ............................................. 49

12. Solution of drawn steel........................................... 50

13. Solution of soft steel.............................................. 51

14. Solution of drawn steel........................................... 53

15. Solution of drawn steel........................................... 55

16. Solution of tempered and soft steels ............................:. 57

17. Digest for originally soft wires ................................... 59

18. Digest for wires annealed in air................................... 60

19. Digest for hard wires ............................................ 60

20. Hydroelectric effect of tensile strain, iron......................... 65

21. Hydroelectric effect of tensile strain, German silver............... 66

% 22. Hydroelectric effect of tensile strain, hrass ....................... 67

23. Hydroelectric effect of tensile strain, copper...................... 67

24. Hydroelectric'effect of tensile strain, iron ........................ 67

25. Hydroelectric effect of stretching, brass .......................... 68

26. Hydroelectric effect of stretching, iron ........................... 68

27. Hydroelectric effect of stretching, miscellaneous.................. 68

28. Digest ........................................................... 71

29. Digest ............................................... 1........... 71

30. Longitudinal uniformity of temper................................ 76

31. Mass constants of glass-hard steel rods ........................... 77

32. Specific resistance of glass-hard steel rods ........................ 77

33. Specific resistance of glass-hard steel rods ........................ 78

34. Viscosity of electrolyzing glass................................... 83

35. Viscosity of electrolyzing glass................................... 83

36. Viscosity of electrolyzing glass................................... 84

37. Resistance of glass across the lines of stress....................... 87

38. Resistance of stressed glass at 100°............................... 87

39. Resistance of stressed glass at 180°............................... 89

40. Resistance of stretched glass at 100°.............................. 94

41. Resistance of stressed glass at 100°. ............................... 95

42. Longitudinal extension of the tubes.............................. 96

43. Resistance of stretched glass at 360°.............................. 98

11
12 . TABLES.

Page.

TABLE 44. Energy potentialized in tensile strains............................ 103

45. Variation of density of stretched wire............................. 104

46. Successive stretching.............................................' 106

47. Energy potentialized in tensile strains....................:....... 107

48. Apparent effect of pressure on resistance of glass.................. 115

49. Apparent effect of pressure on electromotive force................. 116

50. The insulation and pressure coefficient of sperm oil................ 118

51. Behavior of gasoline under pressure .............................. 119

52. Insulation and pressure coefficient of petroleum................... 119

53. Insulation of pressure coefficient of thin mineral machine oil...... 121

54. Pressure coefficient of glass surrounded by mineral machine oil.... 121

55. Insulation of pressure coefficient of sticky mineral machine oil.... 123

56. Breakdown of resistance in case of oils examined.................. 123

57. Breakdown of resistance in case of glass .......................... 123

58. Allowance for increments of electromotive force................... 132

59. Bate of thermal variation of pressure coefficient................... 134
LETTER OF TRANSMITT-AL.

% DEPARTMENT OF THE INTERIOR,

U. S. GEOLOGICAL SURVEY,

DIVISION OF CHEMISTRY, 

Washington, D. 0., August 31,1891.

SIR : I transmit herewith a manuscript by Dr. Carl Barus entitled 

"The Mechanism of Solid Viscosity," with the request that it be published as a bulletin of the Survey. It represents work done in the 

physical laboratory.

Yery respectfully,

F. W. CLARKE,

Chief Ohwnist. 

Hon. J. W. POWELL,

Director.

13

PREFACE.

In the following pages I have brought together such of my experiments on the viscosity of solids as have an immediate bearing on the 

molecular mechanism by which viscous motion in solids is promoted. 

The bulletin is therefore a continuation of the previous publication 

(Bulletin 73), in which the phenomenon of viscosity was considered 

more particularly with reference to its physical manifestations. Most 

of the chapters of the present work are short, and a preliminary survey 

of the work done can be expeditiously made by consulting the table of

contents,

C. B. 

15

THE MECHANISM OF'SOLID VISCOSITY.

BY CARL BARTJS.

CHAPTER I,

TENSILE, DRAWN, AND OTHER STRAINS IN THEIR BEARING ON 

MAXWELL'S THEORY OF VISCOSITY.

INTRODUCTORY.

1. It is known that the effect of drawing metallic wires through 

a draw-plate is a marked decrease of the viscosity of the originally soft 

metal. The diminution increases with the intensity of strain imparted. 

It is not so well known that the viscous effect of a tensile strain applied 

in any degree to the same originally soft metal is after straining almost 

nil in comparison. Kohlrauscji, 1 and his pupils, Streintz2 and others, 

more recently and in extensive researches Mr. Herbert Tomlinson,3 

have occupied themselves with these phenomena. The,results of these 

observers are in general accord, and agree well enougli \vith my work 

that special publication of new data might appear superfluous. Nevertheless, as steel has been but sparingly dealt with, and as results fitting 

at once into my diagrams are essential to my purpose, I have found it 

desirable to communicate them. Apart from these considerations the 

observations which I need must be made with minute reference to Maxwell's theory. In this respect the earlier work is seriously lacking.

The striking difference in the permanent viscous effect produced by 

the action of the two strains is particularly surprising, because the 

strains are imparted by mechanical processes not altogether dissimilar. 

The action of wire-pulling, however, accompanied as it is by surface 

compression as well as longitudinal extension, is conducive to the permanent retention of high-strain intensities, because it imparts to the 

wire an arched structure. In steel, at least, there is a dense shell surrounding an unusually rare core in such a way that the density of the

1 Kohlrausch's original and fundamental researc'ies are given in my earlier papers. Here I need 

refer only to Schroeder, Wied. Ann., vol. 28,1886, p. 354.

2 Strointz, Pogg. Ann., vol. 153,1874, pp. 395,396,411.

8 H. Tomlinson, Phil. Trans., 1886, vol. 2, pp. 801 to 837. The variety of strains and metals examined 

in this paper give it unique value as regards the subject of the present section.

Bull. 94 2 17
18 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

whole mass is materially lessened.1 Conditions favorable to the retention of high-strain intensities are also conditions favorable to the 

occurrence of molecular instability. Hence the marked loss of viscosity of a drawn wire, as compared, caet. par., with a soft wire. This 

premised, it appears that in the case of a wire hardened by simple traction the strain retained after traction is of insufficient intensity to be 

accompanied by marked molecular instability. More rigorously: if the 

wire during traction has experienced a strain S, which strain after the 

tensile stress is withdrawn diminishes to S' (S>S') ? then the wire need 

exhibit no change of viscous quality. For in the above cases of thermal annealing and torsioual motional annealing (§§ 2, 9), the greater 

tensile strain S, supposing its action sufficiently prolonged, has wiped 

out all motional instability for strains S'<S; so it follows here that to 

evoke viscous deformation by aid of tensile strains, the wire must be 

examined during traction, and preferably under conditions of strain 

near the limit of rupture.

APPARATUS.

2. The apparatus used in these experiments is shown in Fig. 1, in 

which ab and cd are the two steel wires-to be counter-twisted. The 

system is fastened above and below to two massive torsion-circles, A 

and B, respectively. The inner ends of the wires are joined by a strong 

brass rod be, carrying a symmetrical circular platform near the lower 

end, on which the lead scale-weights 0 C' C", etc. (4 kilos, to 5 kilos, 

each) may be supported. In order to«facilitate quick work, the connecting rod be is provided with a pair of cross-vanes, D, D', submerged 

in the water contained in an annular trough, fgilif'g'i'Ji'. Finally, the 

mirror m adjustably attached to the rod be (readings by telescope and 

scale) indicates the difference of viscous motion of the two wires in 

consequence of a fixed rate of twist stored between A and B. I may 

add that the rod be can easily be chosen light enough, compatibly with 

strength, to introduce no viscous effect of its own.

DATA FOE, DRAWN WIRES.

3. The data to test the above are given in the following tables, of 

which Nos. 1, 2, 3 exhibit the behavior of some drawn steel wires. In 

each case the comparison is made with my steel normal No. 15 (the 

lower wire in Fig. 1, An. 450° and twisted to permanent viscous qualities). The drawn wire in Table 1 is in the moderately resilient bright 

commercial state, very soft to the file. The wire in Table 2 has been 

drawn down from a larger diameter and the same state of hardness to 

an extreme of brittle resilience. The wire of Table 3 finally was first 

softened by heating to redness in air and then drawn down to brittle 

resilience. Dimensions are given in the tables, p being the radius and I

1 Cf. Baumeister: Dissert., Wiirzburg, 1883.
BAIIUS.] COMPARISON OF TORSIONAL DEFORMATIONS. 19

and I' the lengths of the wires. L = I + 11 . The impressed rate of twist 

in radians is given under T. The observed permanent torsion is Z(<p-{-<?'). 

o and o' are the temperatures of the drawn and normal wires respec3Tig. 1. Apparatus for comparing viscous deformations.

tively. The former is constant, the latter (0'} at first 30°, and then 

100° j so that tl^e examination is made at two temperatures, in order 

to compare corresponding viscous effects of the drawn strain and of 

temper. As will be more fully shown below, § 5, r-|-2(?> + ?> / (=27r/.L, 

and^f <f>')/?is the viscous deformation indicated by the mirror, per 

unit of length of system, per unit of T. It must be borne in mind (cf. 

§13) that(?> <p')/r is a function of r, for which reason the same rate of 

twist is applied to the wires throughout; applied, moreover, positively 

and negatively for each value of 0'. Finally, after testing the wire in 

the drawn state, it was softened by heating to redness in air and again 

tested. In this case viscous motion at the mirror nearly ceases, thus 

affording an excellent check on the validity of the experiments,
20 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94, 

TABLE 1. Viscosity of hard-drawn steel wire compared ivith soft.

2p = -082cm. ; L=Z+Z' = 30cm. +30cm.

Wire drawn moderately resilient.

e 

6'

30

30

30

30

100

30

100

30

T

2(<mo

+ -1041

-t- -0037

 -0989

Time.

h. m.

1 36

38

39

44

48

1 51

53

54

50

 -0058

+ -0989

+ -0058

 -09J1

 -one

59

63

2 24

26

27

29

32

36

2 39

41

42

44

47

*-*'

 -X103

 00

1-08

3'33

4-43

 -00

-1-01

 2-35

 3-58

-4-61

 00

2-83

6-53

10-23

13-60

 00

3-03

7-07

10-77

Same wire anaealed at red heat in air.

e

6'

30

30

30

30'

100

30

100

30

T

2(0+*')

+ -1034

+ '0014

 1019

- -0028

+ -1047

+ -0000

 -1004

 -0043

Time.

h. in.

3 08

10

11

13

16

20

3 22

24

25

27

30

34

4 00

02

03

05

08

12

4 13

15

16

18

21

*~*'xio»

T *

+ 00

 10

 07

 10

 14

+ -00

 00

 03

 07

 07

 00

 33

 78

1-31

1-44

 00

 33

 88

1-65
UAHTJS.] . VISCOSITY OF DRAWN STEEL. 21

TABLE 2. Viscosity of liard-dravin steel wire compared with soft.

2p=-082cni.; L=Z-H'=30cni. +30 cm.

Wiredrawn (2p=r-13cm. to -08 cm.) 

very resilient.

9

. 6'

30

30

30

30

,,

100

30

100

30

T

2W+*1 )

+ -0959

+ -0087

 0916

 0131

+ -0916

+ -0131

 0873

 -0175

Time.

h.m.

5 52

54

55

57

60

63

6 30

6 32

34

 35

37

40

44

6 52

53

54

55

56

56-7

6 58

59

60

61

62

63

^T X 103

 00

4-37

10-10

15-68

19-46

34-47

- -oo

 4-72

 10-50

 16-16

 20-88

 00

16-80

27-30

34-50

39-05

 -00

 16-80

 26-30

 33-70

 39-40

Same wire annealed -at red heat in air.

0 

0'

30

30

30

30

100

30

T

2(*+*')

. -1019

 0028

+ -1034

+ -0014

 1019

- -0028

Acci

Time.

h.m.

1 32

34

35

37

40

44

1 45

47

48

50

53

57

2 00

02

03

05

08

12

dent.

*-*'

^X103

- 00

* '13

 '17

 20

+ 00

 ]0

 10

 15

 21

 -00

 -47

 -91

 1-28

5
THE MECHANISM 01? SOLIt) VISCOSITY.

TABLE 5. Viscosity of hard-drawn steel wire compared ivith soft. 

p = -082; i=i'=cm.; 6=fl' 30°. Wire drawn (2p='13 to -08 cm.) very resilient.

(2*+*')

+ -099 '

*

+ 006

 099

 090

Time.'

h. m.

3 40

41

42

43

44

45

46

47

5 02'

 04

05

06

07

08

09

10

12

103 X(<£ f)')/T

 00

3-77

6-39

8-30

9-80

11-10

12-20

 -00

 2-70

 4-65

 6-06

 7-35

 8-40

 9-30

 10-90

2(<m')

+ 099

+ 006

 099

 -006

+ 099

+ 006

Time.

h. m.

5 17

18

19

20

21.

22

23

24

25

5 35

36

37

38

40

45

5 46

47

48

49

50

52

56

lO'XW. </>)/T

 00

2-83

4-44

5-80

6-80

7-70

8-40

9-10

 '00

 2-35

--3-77 ;

 5-80

 8-90

 00

2-10

3-36

4-30

5-73

7-70

In Table 4 I give results for the viscous effect of moderate values of 

tensile strain on a plan identical with the above. The pull on the 

strained wire (the normal being No. 15) is indicated in the first column 

in kilogrames. The maximum pull which these wires will bear was 

computed to be between 30 kilos, and 50 kilos. It was found to be 45 

kilos, in some cases experimentally. Inasmuch as I here apply 8-4 

kilos., the pull applied is 17 per cent to 25 per cent of the load producing 

rupture.
BARtfs.1 VISCOSITY OF STRETCHED STEEL:

TABLE 4. Viscous effect of moderate traction. 

Soft steel wire. 2p = -082cm.; Z=Z'=30cm. ; 0=0'=30°; r=-100.

Pull.

Kilos.

0

2-4

Time.

h. in.

5 13

15

17

20

24

2!)

35

5 30

37

38

40

43

48

52

58

103X«> <f>')/T

 00

 03

 10

 13

 17

 18

 00

 07

='13

 23

 -23

 27

 40

Pull.

Kilos.

4-8

8-4

Time.

A.m.

5 59

C 01

0.1

00

10

23

. 31

6 32

47

7 09

23

21 00

10'X«,-4>')/T

 00

 07

 07

 13

 27

 40

 00

 27

 27

- 07

The results of Tables 1, 2, and 3 clearly show the marked influence 

of the drawn strain in effecting diminution of viscosity. Wires drawn 

only moderately resilient are of the same low order of viscosity as glasshard wires. Again, if the wires are drawn very resilient the redaction 

of the viscosity of the originally soft wire is enormous. To eliminate 

the effect of different degrees of softness, I also drew down a wire after 

heating in air (Table 3). The, results are in accord with Tables 1 

and 2. .

Some insight into these results is expeditionary obtained by constructing tangents at like time-points of the curves. This is approximately done in the small summary following (Table 5), by subtracting 

the values of (y <P')/T for the beginning and end of the second minute 

after twisting. Similar values for stretched-wire are given in the last 

two columns, kg. denoting the load.

TABLE 5. Digest for the hard and soft wires in Tables 1, !2, 8, and 4.

30

30

100

100

+ 10

 10

+ 10

. 09

Drawn.

d> A' A -T- - x lo1

1-08

 1-01

2-83

 3 '03

Soft.

<£ </>' A- X 101

T

 10

 00

 33

 33

30

30

100

+ 10

 09

+ 09

100 -09

Drawn.

<f> </>' A------- X 103

4-37

 4-72

10-50

 9-50

Soft.

<j> <y ^ ^- x 10'

 00

 10

 47
24 THE MECHANISM OP SOLID VISCOSITY. [BULL. 94. 

TABLE 5. Digest for the hard and soft wires in Tables 1, S, S, and 4 Continued.

30

30

30

30

30

+ 10

 10

+ 10

 10

+ 10

Drawn. «*

<t> V

+2-62

-2-70

+1-61

-1-42

+1-26

kg0

2-4

4-8

8-4

 10

 10

 10

 10

Stretched.

* </>' tF ^-x io3

+ 03

+ 06

+ 07

From this table the small effect of traction in case of loads below 

25 per cent of the breaking stress is specially manifest; an effect negligible in comparison with the diminution of viscosity due to the drawn 

strain. For the-sake of orientation I may assume that correspondingvalues of A(y <f')/T for glass-hardness wouldat 30° be about 1/103 to 

2/103 that is, about equal to this quantity in the case of a moderately 

resilient wire. In general, the results for the drawn strain both at 30° 

and at 100° corroborate and accentuate the results already obtained 

for temper1 , so that the further discussion can be made as in my earlier 

papers, and may be waived here. I add only that the effect of drawing 

incase of steel is a decrease of the density of the soft metal; for instance,

A. B. c. 

7-76 7-72 7-68 

7-72 7-64 7-64 

7-80 , 7-73

Rods.

Originally soft . . . 

Drawn very resilient . 

Softened after drawing

It appears that in this respect also tile drawn strain and temper are 

similar.

DATA FOR STRETCHED WIRES.

 %

4. Returning to the case of simple traction, the changes of sign of 

(<P <ft)/r suggesting increase of viscosity for loads slightly greater than 

5 kilos., indicate that here, as in the case of motional annealing due to 

torsion, the initial effects are' an increase of viscosity. Nevertheless, 

the obscurely small viscous variations due to traction do not admit of 

interpretation, unless supplemented by data for very much larger loads. 

Again, it is desirable and quite feasible, by aid of the apparatus discussed above, to operate cyclically; in which case the results must be 

such as to bear on the lag-quality of solids under stress.

In the following table (6) I have therefore inserted some data for 

larger pulls. Traction increases successively as far as 90 per cent of 

the breaking stress. It will be superfluous to give more than a few. 

typical examples; and the tables can be further abbreviated, because in 

the stress-decreasing phase of the cycles the viscous effect of loads P

1 Phil. Mag., 5th. ser., vol. 26,1888, p. 205 et seq., cf. Bull. 17. S. Geol. Surv. No. 73, Chap. HI, 1891.
KAHUS.] VISCOSITY OF CYCLICALLY STRETCHED STEEL. 25

below the maximum employed is nil, § 1, and therefore sufficiently 

given by the final load zero. To retain a fixed rate of torsion, T, it is 

necessary to twist the wires anew after each of the larger loads; in 

other wards, to bring back the same scale-division into the telescope at 

the outset of each experiment. Otherwise the torsion seriously decreases in consequence of the rapid viscous deformation of the loaded 

wire.

TABLE 6. Viscous effect of cyclic traction.

Soft steel. 2p = -081 centimeters; I = I' = -30 centimeters.

p

Kg.

0

9

18

27

36

40

40

40

0

Had. 

 10

 10

 10.

 10

 10

 10

<*)

(*)

(*)

Time.

h.m. 

11 31 

33 

40 

51

11 52

53 

 56 

59 

64

11 64

67 

71 

83

12 24 

27

30 

37

12 39 

40 

46

53

12 53 

55 

60 

05

78

1 22 

23 

25 

27

30

1 32 

35 

37

39

1 51 

52 

55

3 30

Kind.

+ -00 

+2-16 

-f3'35

+ -00 

+ -23 

+ -45 

. + -52

 00 

 -12 

 -37

 -00

 -37 

 -48

 -00 

 1'64

 2-53

 00 

 2-98 

 5-07

 9-62

(0_0')X166 

-- 0 

 1440 

 1750

 2120

 0

 200

 390

 00 

+ '30

+1-10

P

Kg.

0

9

18

27

36

40

0

0

 Had. 

+ 13

+ 13

+ 13

+ 13

+ .-13

+ 13

+ 13

+ 13

Tune.

h. m. 

10 22 

. 28 

31 

36

44

10 45 

46 

49 

52

' 55

10 56 

59 

61

65 

68

11 09 

10

13 

16 

19

11 20

21 

24 

27 

30

11 31

34 

36 

38 

41

11 42

45 

50 

60

12 01

04 

09 

13

\/ 1 M

Kad.

 00 

 00 

 00

 00 

 38 

 55

 63

 00 

 05

 08 

 12

 00

 45

 78 

1-04

 00 

1-90 

3-37 

4-01

 00 

"2-71 

4-84 

7-58

 00 

 09 

 09

 00 

 13

 27

Twisted again.
THE MECEtANISM OP SOLID VISCOSITY. [BULL. 94.

TABLE 6. Viscous effect of cyclic traction Continued. 

Soft steel. 2p = -081 centimeters ; Z=Z' = -30 centimeters.

p

Kg.

20

29

T

Had.

+ 13

+ 13

Time:

h. m.

12 14

15

18

22

-24

28

12 30

31

33

36

40

44

<h 'j> ^T^XIO3

Had.

 00

 00,

 05

 07

 09

 00

 11

 25

 33

 44

P

Kg.

38

42

T

Bad.

+ 13

+ 13

Time.

h. in.

12 45

47

50

53

56

60

1 01

04

07

10

13

17

* *'

-~ x io3

Rail.

 00

1-53

2-67

3-79

5-21

 00

9-1

14-9

19-8

25-1

Wire breaks at P = 4G kg.

In adding the successive loads care was taken to avoid vibration 

and jarring; but without special machinery it is impossible to protect 

the" system completely against it. To this cause I attribute certain 

irregularities of sequence which, these and others of my results exhibit. 

Their general significance is none the less definite. The effect of traction is diminution of viscosity, increasing at an accelerated rate in proportion as stress approaches the limit of rupture. Indeed, by sufficiently increasing stress, viscosity may be diminished in any degree 

whatever. The singularly curious feature of these experiments is this: 

that with, the removal of load the viscous effect of traction almost entirely vanishes. It is in this respect that the present experiments bear 

directly on. the truth of Maxwell's theory; for it is only during the 

interval within which conditions favorable to molecular break-up are 

forcibly maintained that the wires exhibit a low order of viscosity of a 

sufficiently marked degree to compare with, the viscous effect of drawn 

strains and of temper, where instabilities are structurally retained.

It follows, in general, that slight applications of mechanical treatment 

(twisting, traction, etc.), inasmuch as they decrease in number the 

motionally unstable configurations of the soft wire, increase viscosity 

(motional annealing). If this treatment is intensified beyond a critical 

stage in other words, if stress is increased sufficiently beyond the limits 

of resilience and toward the limits of rupture then viscosity is again 

seriously decreased. For the action of stress has now become such as 

to introduce its own specific instability, whereby viscous deformation 

is again promoted.

INFEEENCES.

5. Having thus substantiated the remarks of § 1, and shown that the 

accordant results of the earlier observers and my own are such as fol-
BAllDS. VISCOSITY OP STRAINED STEEL. 27

low naturally from Maxwell's theory, it is expedient to give a graphic 

representation of the more important differential data (i. e., differences 

between strained and soft metal for each case of stress) in hand: In 

figure 2 the viscous deformation (<p </>')/?} produced by the action of 

a fixed rate of twist r, is represented as ordinate, time as abscissa. 

The material is steel, the originally soft state of which has been transformed by temper (glass-hardness), drawn strain (wire-plate), tensile 

strain, and torsion respectively. Curves are given for intense values 

and for moderate values of stress. The nature of the problem precludes greater definiteness as to stress data. In case of traction infinitesiinally below the point of rupture, for instance, viscous deformation would occur with such extreme rapidity that its diagrammatic 

representation would be a vertical line.

Again, in case of traction of sufficiently small value, the curve would 

be a horizontal line coinciding with " soft," or even a curve below it 

(motional annealing). In a measure this is true of the other strains; 

and I have therefore expediently inserted the values for deformations 

actually found.

The general outcome of the present, paper is this, that the-effect of 

strain of whatever kind, applied in sufficient intensity to-homogeneous 

soft steel, is marked diminution of viscosity. Again, inasmuch as the 

underlying cause of viscous deformation is the occurrence of unstable 

configurations the number of which is being reduced in the course of 

viscous motion, Maxwell's theory naturally suggests the applicability 

of exponential equations for the description of the time relations of 

such motion. From, another point of view it appears that.the loss of 

viscosity experienced by a given metal, under action of a given kind 

of strain, may not inappropriately be used as a measure of its intensity. 

Finally, the curious observation, that in all the cases given loss of viscosity has taken place simultaneously with increase of hardness, is one 

of the suggestive results of the experiments made.

Quite recently Auerbach, 1 in applying a method for the absolute 

evaluation of hardness due to Hertz, has shown that hardness and 

elasticity are associated quantities, i. e., quantities between the corresponding variations of which a close agreement is maintained irrespective of the body operated on. Hence the above results show a 

fundamental distinction between viscosity and elasticity.

From experiments made on the behavior of iron in passing through 

the temperature of recalescence Osmond 2 was led to conclude that 

all the phenomena of hardness are due to a second or /? variety 

of iron. This /5 iron may be formed from ordinary or a iron, either 

spontaneously by heating above a certain high temperature, below 

which, however, it is unstable and passes back to «iron on cooling

1 Auerbach: Wied. Ann., vol. 43, 1891, p. 61. Other references are there given. 

2 Osmond: Annalea des Minos, July-August, 1888, "Introduction," and elsewhere. CT. Bull. U. S. 

Geol. Surv. No. 73, p. 51, 1891.
28 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

except under certain conditions, or /? iron may be formed artificially 

by the action of pressure of any kind applied below the critical temPig. 2. Time variation of viscous deformation, in case of soft steel transformed by temper, drawn* 

strain, traction, and torsion, respectively. The abscissa represents the soft or unstrained wire.

perature in question. The presence of carbon (steel) and rapid cooling 

is specially favorable to the production of /? iron, and the presence of
OSMOND'S THEORY OF HARDNESS. 29

this substance manifests itself in the resulting hardness of the metal. 

Now it is to be observed that the above observation on the similarity 

of viscous eifects of all kinds of strain, \vhether tempered or mechanically applied, is in harmony with Osmond's theory. Again, the acknowledged instability of/3 iron at ordinary temperatures supplies the 

requisite unstable configurations in virtue of which, following MaxAvell's theory, viscosity is reduced. This theory of Osmond, however, 

either proves too much or it is a suggestive working hypothesis relative 

to the behavior of other metals. For. the results of Streintz, Tomlinson, and myself, cited above, show that in most if not all metals viscosity is reduced by the presence of marked intensity of mechanical 

strains. Certainly metals are capable of being hardened by traction, 

the draw plate, torsion, etc., although no phenomenon corresponding 

to Gore's phenomenon in. iron has been observed. Osmond's theory of 

a change of molecule of iron by mechanical action therefore calls for 

experiments relative to the definite discovery of the « and ft varieties of 

metals other than iron, nickel, and a few more^ before the standpoint 

taken can be maintained.

An important inquiry is thus suggested which would lead ulteriorly 

to a test of Osmond's theory: It is to be found whether the maximum 

of drawn strain which the wire of a given metal can retain is (cset. 

par.) a function of the viscosity of the metal; or whether the strain retained is largely independent of viscosity and subject to other conditions. In the last case retention would be conditioned by a chemical 

mechanism, and Osmond's theory would therefore be substantiated at 

once.

I may state in concluding that Qsmond's views are not wholly new, 

having been suggested in their general bearings in a remarkable thermoelectric investigation by F. Braun.1

IP. Braun: Phil. Mag, (5), vol. 19,1885, p. 503, § 8.
CHAPTEE II.

THE TWO SPECIES OF MOLECULAR BREAK-UP WHICH PROMOTE 

VISCOUS DEFORMATION.

INTRODUCTORY.

6. Following the argument which underlies Maxwell's theory of solid 

viscosity experimentally, I was"obliged to take cognizance of two causes 

which promote viscous deformation in solids.1 For any structure will 

give way under impressed conditions of stress, as a whole or in part, 

because either the cements or the bricks are insufficiently strong to withstand it. Similarly the underlying cause of viscous motion is either 

such structural change in which groups of molecules pass without loss 

of identity from an initial to a final configuration, or it .is a break-up 

superinduced by the disintegration of one or more molecules of each 

group. Whichever the change may be, it must, from the nature of the 

problem in general,, be distributed uniformly throughout the mass of 

the solid (§ 14). Even without stress the said change may result from 

secular subsidence. Moreover it is conceivable that molecular disintegration may occur in such a way as to elude detection.

Now I have since been able to prove experimentally that in glasshard steel a change of the viscous quality may be obtained as the result 

of at least two distinct kinds of structural change, probably as the result of the two kinds of break-up in question. The present chapter purposes to show this by aid of the phenomena of accommodation, or motional annealing, as they may be called more uniformly in keeping 

with the following work,

MOTIONAL ANNEALING DEFINED.

7. The term annealing or tempering, in its most general sense, refers 

to a process by which strained solid structure, whether maintained by 

mechanical or chemical causes, is changed to isotropic structure. In 

viscosity, inasmuch as strained structure is ultimately accompanied by 

molecular instability, annealing is a process by which viscosity is increased; and from this point of view annealing need have no direct 

reference to exposure to temperature. Hence IJiave designated by the 

term motional annealing all such forced molecular motion to and fro, in 

virtue of which the molecules of a thoroughly soft solid are brought into 

new relations°to each other, to the effect that viscosity is increased at

»Phil. Mag., November, 1888. 

30
VISCOSITY AND ELECTRIC RESISTANCE OT STEEL. 31

the expense of the motionally less stable configurations of the soft 

solid. There may appear to be some incongruity in the term, inasmuch 

as the solid motionally acted on always experiences strain; it is not the 

strain, however, but the increment of viscosity of the solid, to which 

the term refers.1

Again, in order that a solid maybe motionally annealed the mechanical treatment (torsion, traction, etc.) must be applied below a certain 

critical limit of intensity. Otherwise this treatment introduces its own 

specific instability; and in proportion as stress is indefinitely increased 

the viscosity of the solid may nowo be reduced in any measure. Further justification of the term, is to be given in §§ 11,14. At present it is 

more expedient to indicate the points of crucial difference between motional annealing and thermal annealing in their effect on steel in the 

glass-hard state.

STRAIN, ELECTRIC RESISTANCE, AND VISCOSITY.

8. When glass-hard steel is annealed at 100° the effect is a decided 

increase of viscosity amounting to almost one-half of the total viscous 

interval, hard-soft.2 This marked increment of viscosity is accompanied by an equally striking electrical effect.3 For it has been shown 

that the specific resistance of hard steel diminishes as much as 15 per 

cent as the result of annealing at 100°. Finally, since the electrical 

effect is a sufficient indication of the changes of volume (decrement) 

and-of carburation, it appears conclusively that the underlying cause 

of -the increase of viscosity here in question is a disintegration of the 

unstable carbide molecule of steel.

TEMPER, ELECTRIC RESISTANCE, AND VISCOSITY.

9. Again, an increment of the viscosity of glass-hard steel comparable in magnitude with that of annealing at 100° may be obtained without heat. It is merely necessary, for instance, to apply to the glass- 

.hard wire large enough rates of twist, a sufficient number of times 

alternately, in opposite directions. This method of increasing viscosity 

has no electrical concomitant comparable with the electrical effect of 

§ 8. Hence the underlying cause of the observed increase of viscosity 

in this case is probably not a disintegration of the carbide molecule of 

steel, or, at least, a disintegration quite unlike that of the foregoing 

instance.

DATA RELATIVE TO TEMPER, ELECTRIC RESISTANCE, AND VISCOSITY.

10. In the following tables (7 and 8) I give the data necessary to 

substantiate § 9. The method 4 of experiment being identical with the

 PhiL Mag., 5th ser., vol.^26,1888, pp. 199 to 203.

» Am. Jour. Sci., 3d ser., vol. 33,1887, p. 26; Phil. Mag., 5th ser., vol. 26,1888, p. 188, et seq.

8 Bull. IT. S. Geological Survey, No. 14, p. 49,1885. 

4 Phil. Mag., 5th ser,, vol. 26,1888, pp. 189 to 191. The use of differential methods premises that the 

viscous deformations of all the wires to be compared are similar time functions. That this is the case 

must be verified preliminarily by some absolute method.
32 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

one described in verifying § 8,1 need only to call to mind here that my 

normal steel wire (maximum viscosity) and the fresh glass-hard wire 

(minimum viscosity) were countertwisted; that the ends of the vertical 

system were fixed, and a mirror-index placed near the middle, at the 

junction of the two wires. 1 Of. Fig. 1, § 3. Table 1 contains the results 

for viscosity, both wires being at the same temperature 0. The impressed rate of twist is given in radians under r, and the permanent 

torsion observed at the close of each experiment under 2(</> + /). Since 

the lower end of the system was twisted 360°, r + 2(<p + /), 2,x/L, 

where L is the length of the two'-wires. Finally, (<p <p'}/r is the viscous motion at the index, per unit of r, per unit of L, at the time specified. In other words, 2<p and 2<p' refer to the'hard and the soft wires, 

respectively, and denote angular viscous motion of one right section 

relatively to another, when their distance apart is 1 cm. of length 

of wire. (<p ^')/T nee(i n°t be independent of r. (§ 13.)

Table 7 indicates that the wires were twisted eight times alternately 

in opposite directions. Before and after each series of viscous measurements in Table 7 the resistance of the glass-hard wire was measured 

by a special device utilizing Matthiessen and Hoskin's method. These 

results are given in Table 8, where rt is the observed resistance in microhms, Ar« the variation from the final value, rt = 39500.

TABLE 7. Viscous effect of motional annealing. Glass-hard steel. 

6 = 29. L = 30 cm. + 30 cm. Diameter of wires, 2p = -081 cm.

Twist 

No.

1.

2.

3.

4.

T

2(* + *')

<,

+ 0992

+ 0055

 0983

 0064

+ 1021

+ 0026

 1021

 0026

Time.

h.m.

2 25

36

32

35

38

40

2 49

51

53

56

63

3 07

09

11

14

21

3 24

27

29

32

37

*-*'xl03

+ -oo

 94

1-99

2-79

4-45

 -00

 1-95

 3-97

 5-93

+ -00

1-01

1-99

3-36

 -00

 -91

 1-85

 3-06

Twist 

No.

5.

6.

7.

8.

T

2(0 + <£')

+ 1021

+ 0026

 1018

 0029

+ 1018

+ 0029

 1018

 0029

Time.

h. in.

3 40

42

44

47'

52

3 55

57

59

62

67

4 09

11

13

16

20

4 23

25

27

30

37

<t>-<t>'

^~X103

+ -co

 68

1-38

2-19

 -od

 -74

 1-44

 2--39

 00

 64

1-28

1-89

 -00

 -64

 1-28

 2-32

iSee Bull. U. S. Geol. Survey No. 73, 1891, pi. I, p. 54.
BARUS.] THE TWO KINDS OF MOLECULAR BREAK-UP.

TABLE 8. Electrical effect of motional annealing. 

Glass-bard steel, 2p = -081 cm.

33

Twist 

]STo.

0.

1.

2.

3.

4.

T

0

 099

+ 098

 102

+ 102

rt

39550

39380

39350

39570

39430

&rt

+ 50

 120

 150

+ 70

 70

TwistNo.

5.

0.

7.

8.

T

 102

+ 102

 102

+ 102

rt

395CO

39530

69500

39510

An

+60

+30

+00

+10

DISCUSSION OF RESULTS.

11. The results of Table 7 .are in excellent accord with my earlier 

data; and the oscillatory march of the viscous increment can be represented in the same way, If the tangents be constructed at the same 

time-point, in each of the curves of Table 7 there appears to be some 

similarity between the march of these results (A(? </>')/?) and the corresponding inarch of rt in Table 8. But interpreted by the data of. § 7, 

this similarity is only qualitative in kind. In other words, whereas 

fche increment of viscosity due to successive alternations of twist is decidedly greater than one-half of the increment of viscouty due to 

annealing glass-hard Steel at 100°, it appears that the electrical effect 

in the first instance (motional annealing) is practically negligible in 

comparison with the electrical effect of thermal annealing. In Table 8 

the total interval of variation of Ar( is about one-half per cent of rt ; on 

the other hand, the variation of rt due to annealing at 100° is from 10 

per cent upward. It follows that in glass-hard steel there are two 

distinct ways in which viscosity may be appreciably increased, a result 

corroborating §§ 8, 9. Again, if the possibilities of viscous motion are 

to be fully given, it is essential to postulate groups of atoms, as well as 

the somewhat less definite groups of molecules, both varying in degrees 

of stability from point to point of the solid mass. Hence slight positional change of the elements of the atomic configurations, or of the 

molecular configurations, due either to stress not exceeding a critical 

value or to mere secular subsideuce, must in general involve an augmentation of the viscous quality.

DATA FOR CYCLIC TWISTING-.

12. Having arrived at this result I desire to inquire somewhat more 

in detail into the viscous relations of the motional effect, §§9,10. This 

is attempted in Table 9, in which torsional stress is a,pplied cyclically. 

The viscous behavior is studied at each of these successive stages of 

increase or decrease, as shown in the first column, r, of the table. As 

before, the length of the system of two wires, L = Z + /'=30 cm.+ 30 

cm.; diameter, 2/> = -081 cm. The .final column, A(e> <?'}, being the 

detorsion from the beginning to the end of the first minute after 

Bull. 94 3
34 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

twisting, may be taken as an index of the rate of deformation. In the 

first and second cycles twist is imparted positively 5 in the third cycle 

negatively. To follow the sequence of observations it is sufficient to 

consult the time column.

TABLE 9. Viscous deformation in case of cyclic twisting. 

FIRST CYCLE.

Twist increasing.

Eate of 

twist, r

 000

 009

 017

 035

 043

.nco

Time.

h. in.

37

38

39

40

10 41

42

43

44

45

10 46

47

48

49

50

10 51

52

53

54

55

10 56

57

58

59

60

11 01

02

03

04

05

(*-*') X106

0

3

5

6

0

9

15

20

0

14

23

27

0

31

51

67

0

45

77

100

0

36

69

103

A-*' ^^jT^-XlO3

 0

1-1

1-5

1-9

 o

1-4

2-8

3-2

 o

1.5

2-5

2-8

A(*-*') 

X106

3

9

14

Twist decreasing.

Eato of 

twist, T

 000

 009

 017

 026

 035

 043

 052

Time.

h. m.

19 31

32

33

34

35

1 18

30

12 26

27

28

*29

30

12 21

22

23

24

25

12 16

17

18

19

20

12 11

12

13

14

15

07

08

09

10

12 01

02

03

04

05

(0-^')X106

0

 10

 20

 27

 107

 120

0

 8

 15

 21

0

 5

 12

 17

 0

' - 7

 12

 15

0

 7

 13

 15

0

 5

 8

 13

0

 3

 9

 11

A(<A -<*>') 

X10«

10

5

7

7

3
BARU9.] CYCLIC TWISTING. 35

TABLE 9. Viscous deformation in case of cyclic twisting Continued. 

FIRST CYCLE-Ccmtiiraed.

Twist increasing.

Kate of 

twist, T

 061

 070

 078

 087

 096

 105

Time.

h. in.

11 00

07

08

09

10

11 11

12

' 13

14

15

11 16

17

18

19

20

11 21

22

23

24

25

11 26

27

28

29

30

11 31

32

33

34

35

0

60

100

133

0

97

153

207

0

100

167

237

0

117

.197

263

0

137

233

307

0

167

280

397

*-*'..

T

 0

8-8

61

8-2

 0

3-5

5'9

8-3

 0

3-7

C-3

8-3

 0

3'9

6-8

8-9

 o

4-4

7-4

9-6

A «> *')

97

100

117

137

167

Twist decreasing.

Eate of 

twist, T

 001

 070

 078

 087

 096

Time.

h. in.

11 50

57

58

59

60

n

Kl

52

53

54

55

11 46

47

48

49

50

11 41

42

43

44

45

11 30

37

38

39

40

(<t> -(/>') X10G

0

 7

 7

 9

0

 5

 5

- 5

0

 2

 2

 1

0

+ 3

+ 7

+ 10

0

+ 8

+ 21

+ 31

X 10

 7

 5

2

+ 3

+ O
36 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

TABLE 9. Viscous deformation in case of cyclic twisting Continued.

SECOND CYCLE.

Twist increasing.

Eate of 

twist, T

 o

 017

 035

 n^9

 070

 087

 105

Time.

h. in.

1 31

32

33

34

35

1 36

37

38

39

40

1 41

42

43

44

45

1 40

47

48

49

50

1 51

52

53

54

55

1 56

57

 58

59

 60

«>-0')Xl06

0

5

7

11

0

7

13

15

0

7

10

17

0

7

19

30

0

15

30

41

0

67

120

170

d>-<V y^-XIO3

 0

 7

1-2

1-8

 0

 5

1-1

1-2

 0

 3

 5

 9

 0

 3

 7

1-2

 0

 5

 9

1-3

 0

1-9

3-2

4-5

A(*-*') 

X1Q6

j

1

1

7

15

67

Twist decreasing.

Bate of 

twist, T

 0

 017

°,

"035

 052

 070

.AQ7

Time.

h. in.

2 20

27

28

29

30

2 21

22

23

24

25

2 in

17

18

19

20

2

1 1

12

13

14

15

2 06

07

08

09

10

2 01

02

03

04

05

W> -<£>') X 10°

 0

 9

 17

 23

 0

 12

 19

 25

 0

 5

 10

 15

 0

 9

 11

 14

 0

 7

 7

 7

 0

 2

 4

A(*-*') 

X106

9

1O

5

f)

 7

2
nxnus.] CYCLIC TWISTING. 37

TABLE 9. Viscous deformation in case of cyclic twisting Continued. 

THIRD CYCLE. TWIST IN OPPOSITE DIRECTION.

Twist increasing.

Kate of 

twist, T

 017

(\V\

 052

 070

 087

 090

 105

Time.

h.m.

3 24

25

26

27

28

29

3 30

31

32

33

34

3 35

3C

37

38

39

41

42

43

44

3 45

46

47

48

49

3 55

56

57

58

59

4 05

06

07

08

09

((^-^OXIO0

0

12

19

25

28

0

13

32

37

0

43

77

103

0

97

163

213

0

147

240

307

0

117

207

273

0

135

240

313

<4-<f,' ^-^- X 103

 0

1-9

3-0

3'9

4-6

 0

1-1

2-5

2-9

 0

2-3

4-1

5-5

 0

3'8

6-5

8-5

 0

4-7

7-6

9'8

 o

3-4

6-0

7-9

 0

3'6

6-4

8-3

A (*-*') X106

12

13

43

07

147

117

135

Twist decreasing.

Hate of 

twist, T

 0

 070

 087

 096

Time.

ft. in.

4 17

18

19

20

21

3 50

51

52

53

54

4 00

01

02

03

04

4 10

11

12

13

14

((fr-^OXlO6

 0

 28

 45

 63

 0

 1

 1

+ 2

0

+ 5

+ 14

+ 23

+ 0

+ 0

+ 10

+ 27

.

A (*-*') X10°

OQ

1

+ 6

0

DISCUSSION OF RESULTS OF CVCLIC TWISTING-.

13. The marked feature. The first result given by these data is obtained by comparing q> <p' and (cp cp^/T, showing' that the latter 

quantity is not independent of r. Nor can it be asserted that the 

change of (q> <p'}/r with increasing r is retarded. It follows that 

comparable values of (<p q>>}/T are only obtained by keeping r nearly 

constant, as has been done in all my experiments.
38 THE MECHANISM OF SOLID VISCOSITY, [BULL. 94.

Again, the large variations of (<p (pf) in the direct or stress-increasing phase of the cycles, as compared with the corresponding variations 

in the retrograde or stress-decreasing phase of the cycles, together 

With a repetition of the whole phenomenon on a smaller scale for succeeding cycles of the same sign, are features of these experiments. 

When the sign of the twist is reversed, cycles which exceed the original 

one in magnitude are obtained. These in their turn dwindle on repetition of like signs of T. Finally, the influence of residual action in 

case of retrograde cycles appears more clearly in proportion as stress 

approaches zero. On the other hand, the circumflex contours of the 

earlier retrograde curves (T decreasing from -105) is not a mere error 

of observation, but results from superposition of direct and residual 

phenomena. This is specially marked in the third cycle, where stress, 

after r=-087, was applied in a zigzag way, viz:

r XIV = 87, 70, 96, 87,105, 96.

14. Analogy with thermal annealing. The clue for the interpretation 

of the above complex phenomena as a whole is suggested by the data 

for A (cp cp'). It then appears that the viscous behaviour of the wires 

is intimately connected with the amount of permanent set imparted 

during the period of action of stress. From, this point of view the 

phenomena become not only strikingly analogous to thermal annealing 

in case of temper, but of special importance as regards their bearing 

on Maxwell's theory. The following description l applies, mutatis mutandis, to both classes of phenomena:

(1) The viscous deformation (annealing effect) of any stress (temperature) acting on glass-hard steel increases gradually at a rate diminishing through infinite time; diminishing very slowly in case of low 

stress (temperature); diminishing very rapidly at first and then again 

slowly in case of higlr stress (temperature); so that the limit of permanent deformation is approached asymptotically.

(2) The ultimate viscous deformation (annealing effect) of any stress 

r (temperature t), is independent of preexisting effects of the stress r' 

(temperature t'), and is not influenced by subsequent application of 

stress T' (temperature t'), provided T>T' (£>£'). In case of incomplete 

deformation (partial annealing) induced by stress T (temperature t), 

this law applies more fully as the ultimate effect of T (t) is more nearly 

reached. Again, the effect of r1 succeeding r (t1 succeeding t) is more 

nearly nil as the effect of T>T' (t>f) approaches completeness.

To discern the cause of this detailed analogy it is sufficient to call to 

mind, (1) that in thermal annealing viscous deformation is produced by 

thermal diminution of viscosity under conditions of the initially given 

stress stored up in the tempered solid; in motional annealing by increase of the mechanical stress applied from without under conditions 

of initially given viscosity. Finally, (2) the configurations, molecular

i Cf. Phil. Mag., 5th ser., vol. 2G, 1888, p. 214.
hints.! MOTIONAL AND THERMAL ANNEALING COMPARED. 33

Or atomic, which just break up under the action of stress T or temperature t, respectively, are necessarily limited by a higher order of stability, and are greater in number than those just surviving under less intense conditions, of stress or temperature. This is the crucial feature 

of the analogy. However unlike the instabilities may be in the two 

oases of motional and of thermal annealing, however unlike the treatment to which they are here respectively subjected, its effect in modifying tlie occurrence of instability is similar, and hence the similarity of 

viscous results.

So far as I have observed, however, residual phenomena are absent 

in thermal annealing of glass-hard steel, and this is a point of differ* 

ence between the break-up of atomic groups and molecular groups, The 

former are not reconstructed. Again, in motional annealing for increasing rates of twist, thick wires show viscous deformation at earlier 

dates than thin wires. The break-up commences at the external surface, where stress is most intense, and proceeds thence to the axis, 

where stress is least. The history of motional annealing is therefore 

essentially dependent on the dimensions of the deformed wire and varies 

for different values of radius. I pointed out 1 that in soft iron the limits 

of torsional resilience were reached when the obliquity of the external 

fiber (shear) somewhat exceeds .003 radians. Finally, the ultimate annealing effect (time = o>) of any temperature t acting on glass-hard 

steel increases at a retarded rate with temperature, and practically 

reaches the limit of variation below 350°. In case of motional annealing stress may be applied in any degree from without, and increasing 

effects obtained limited only by the given degrees of resilience or of 

brittleness. Nevertheless, if the wire admits of permanent .set, the 

analogy pursued may be pushed even to this extreme detail. For, just 

as in the case of thermal annealing above 350°, no further marked 

effects are produced, because the intensity of stored stress is invariably below the value of viscosity; so in case'of motional annealing, when 

stress surpasses the limits of resilience, further increment of marked 

consequence is no longer elastically retained.

. Jour. Soi., vol. 34, 1887, p. 183.
CHAPTEEIIL

THE EFFECT OF MECHANICAL STRAIN ON THE CARBURATION

OF STEEL.

INTRODUCTORY.

15. Drownds experiments. I shall, in this chapter, endeavor to discuss 

the nature of some shortcomings of the present methods for the estimation of uncombined carbon in addition to the subject matter of the 

superscript. Among earlier investigators Dr. Thomas Drowne 1 has 

made similar observation with reference to cast iron. The stimulus 

of Drowne's work was a remark of Bell's, stating that white and gray 

pig iron differ only in the magnitude of graphitic crystals contained, 

which crystals are fine grained in white pig, and coarse grained iu gray 

pig. To disprove this assertion Drowne cast a sample of iron in a chill 

mold,2 thus obtaining both the white and the gray variety. Analyses 

showed that while these two parts of the same casting did not differ 

much in total carbon, the free carbon in the gray iron was more than 

twice as great in amount as the free carbon in the white iron. He thus 

obtained strong evidence against Bell's statement. Drowne then proceeded to vary the method of treatment by varying the solvent and by 

boiling. He infers that the carbide is not decomposed except by boiling, and accentuates the crudeness of the analytical methods.

IB.'The present method. The above pages have clearly shown that 

the underlying cause of viscous deformation is either a break-up of 

atomic or of molecular configuration. The former phenomenon admits 

of direct proof and does occur in glass-hard steel. The molecular breakup is less easily verifiable, and can not be as clearly defined as the other. 

I have therefore been tempted to question whether, even in the case 

of viscous deformation induced by mechanical strains, the underlying 

break-up is a mere rearrangement of molecules. (Of. § 9.)

Among the more promising methods for deciding this question, the 

plan adopted in the discussion of annealing phenomena 3 suggests itself. 

An exceedingly intimate intermixture of carbon and iron is here presented. Indeed Matthiessen considered it a solidified solution or inix1 Drowne: Trans. Am. East. Mining Engineers, vol. 3,1874-75, pp. 41-44.

a I may refer here to a similar experiment of Karsten's (Eisenhiitteiikuiide, Bd. 1,3 Aufl., 18JI. p. 581, 

(it seq.) from which the distinction between combined and uucombined carbon was originally derived. 

3 Barus: Bull. U. S. Geol. Survey, No. 73, Chap, in, 189].

40
*Anus.] METHOD AND RESULTS. 41

tures of these. Hence the possibility of chemical changes of configuration superinduced by mechanical stress (wire-pulling, torsion, flexure, 

traction, compression) applied from without, is favorably open to experiment. Put in its simplest form, the problem is a determination of 

tlie variation of the amount of the uncombined carbon in steel, produced by stress; for it may be plausibly argued, I think, that such 

disintegration of molecule as is here in question could hardly take 

place without the accompaniment of a carbu ration effect.

METHOD OP EXPERIMENT.

17. The method of procedure, apart from its extreme tedium, is 

sufficiently simple. A soft wire of proper length is cut into halves, one 

of which is dissolved without further treatment, the other drawn down, 

to as small a diameter as feasible and also dissolved. The two samples are then tested for uucombined carbon. I used the customary 

process described by Blair in its most complete form. The Samples 

were dissolved in cold dilute acid, then boiled, after which the carbon 

was collected on Gooch's asbestos filter, duly washed with dilute HCL 

and hot water, KOH, alcohol and ether. It was thereupon dried at a 

temperature of at least 1GO° for a sufficient time, cooled in a desiccator, 

and the difference in weight of the Gooch crucible before and after ignition in oxygen estimated as carbon. This is not as accurate a process as the regular combustion method usually prescribed. But it is 

far more expeditious; and the errors made in weighing carbon directly 

are of very much smaller moment than the solution and other errors 

which I will point out below. Indeed the validity of the whole method 

stands seriously in question, in a number of fundamental particulars: 

and so long as these have not been surely cleared away, refinements 

of carbon measurement are obviously absurd.

RESULTS OBTAINED.

18. My results are given in the following Ta,blc 10. To understand 

them fully, introductory remarks as to the structure of the soft steel 

used in each case are essential. In my first experiments (rods Nos. 1 and 

2 for instance), I drew doAvn the whole wire; then I softened one-half 

of it after drawing, by annealing at red heat in air. On dissol\7 ing, the 

drawn wires were very much more intensely attacked than the freshly 

softened wires; so that the beaker containing drawn wires is turbid 

and black with carbon before the other hardly shows traces of carbon 

precipitate. This result is exceedingly striking and uniform, and I at 

first inferred that the effect of drawing is necessarily a transformation 

of carbon in steel from the combined to the uncombiued state. And yet 

this conclusion, as I afterwards found, does not at all follow. The effect 

of annealing at red heat on the carbon in the steel varies enormously 

with the details of the method. In other words, steels of a given kind 

and nominally soft, may nevertheless differ remarkably in internal struc-
42 THE MECHANISM OF SOLID VISCOSITY. [BOLL. 9i.

ture. If we start with soft steel, annealed by the commercial method 

of excessively slow cooling, and then draw the wires down, it can not 

be assumed thtft the part of the drawn wire which is annealed at i ed 

heat and cooled in air after drawing, is identical with the wire before 

drawing. Indeed, since the rate of cooling increases as the diameter decreases, it follows that two wires annealed at red heat in air must differ 

in degrees of softness and carburation even if all other conditions are 

the same. I desire to emphasize this point for it indicates the first difficulty with which I had to contend.

-v

TABLES.

19. In the Table I have, therefore, inserted the treatment and temper of the wire before drawing in the wire plate, as well as after drawing. The radius /? of the wire is also given for each case.

M is the mass of steel dissolved, in grammes. A larger amount would 

have been desirable, but the rods of best Stnbb's steel come in short 

lengths (33cm ),and as the drawing of each new length nearly doubles 

the labor, I did not care to operate upon greater masses (M) of steel. 

The carbon contained in the M grammes in question is given under m, 

also in grammes, and the final columns contain the values of m / M.

Excepting numbers 27 and 28, the first thirty-four measurements were 

made with a view to testing the steel; the next twenty-one (numbers 

35 to 56) chiefly with a view toward testing the method. In the final 

measurements, the steel again is chiefly considered.

TABLE 10. Graphitic carbon in soft and in drawn steel.

[S, annealed from red heat, with very slow cooling (commercial). SA, heated to redness and cooled in 

air. G-H, glass-hard. An, annealed at 500°. Dr, fresh drawn, usually from iliameter=2p = 0-13C111 

to2p-=0-08"".]

Before drawing.

Original condition.

S .............

S .............

S .............

S.............

S.. ...........

S .............

S ............. 

S ............. 

GH. .......... 

GH. .......... 

S ..............

S ............. 

GH. .......... 

GH. .......... 

GH. .......... 

GH. ..........

Final condition.

s...........

s. ..........

S ...........

s ...........

s ...........

s.... .......

SA......... 

SA ......... 

SA. ........ 

SA .........

s. ..........

SA. ........ 

SA. ........ 

SA ......... 

SA..... ... 

SA .........

2pX103

130 

130 

130 

130 

130 

130 

130 

130 

130 

130 

130 

130 

130 

130 

130 

130

Before dissolving.

Condition.

Dr........

SA -......'

Dr........

An.lb .... 

An.l£h .... 

SA .......

Dr........

SA .......

SA .......

Dr........

s. ........

SA .......

SA .......

Dr........

SA .......

Dr........

2pX10*

80 

80 

80 

80 

80 

80 

80 

80 

130 

90 

130 

130 

130 

80 

130 

80

M

3-10 

3'16 

3-17 

3-14 

2-30 

2-91 

3-04 

2-98 

3-15 

2-96 

3-25 

3-21 

3-17 

2-96 

3-22 

2-74

mXlO3

18-3 

15-4 

15-9 

17-4 

1C-5 

lost 

17-2 

18-0 

14-9 

18-2 

27-1 

22-3 

16-7 

17-4 

19-7 

14-9

2"o

5-9 

4'9 

(?)5-0 

5-5 

5-5

5-0

c-o

4-7

c-i

8-3 

6-9 

5-3 

5-9 

6-1 

5-4

No.

{I

11

<; 5<6

* 8

{ ° 

* 10 5 11

l 12 

CIS 

< 14 

C15 

* 16
BAlttS.] EFFECT OF STRAIN ON CARBURATION. 43

10. G-raphitic carbon in soft and in drawn steel Continued.

[S. annealed from red heat, with very slow cooling (commercial). SA, heated to redness and cooled 

in air. GH, glass-hard. An, annealed at 500°. Dr, fresh drawn, usually from diameter = 2p = 

0-13"" to 2p = 0-08° .]

Before drawing.

Original condition.

S .............

S .............

S.. ......... .

s.............

S .............

s. ............

s. ............

s.............

s. ............

s .............

s* ............

s* ............

s .............

s. ............

GH. ..........

'GH.... ....... 

GH. .......... 

GH. ..........

(t) 

(1) 

(t) 

(!)

Beaker ....... 

Erl. flask, etc . 

Erl. flask, etc . 

Beaker, boiling 

Beaker, boiling 

S .............

S.............

Final condition.

SA .........

SA. ........

s...........

S ...........

S

-

S ...........

s...........

s..... ......

s...........

s ...........

s ...........

s...........

s ...........

s ...........

CJ A

SA......... 

SA. ........ 

SA. ........

HC1 ........

HC1 ........

HC1 ........

HC1 (cone) . . 

HC1 ........ 

HC1 ........

HC1 ........

HC1 ........

HCl ........

S...........

S ...........

2pX10«

130 

130 

130 

130

130 

130

140 

140 

140 

140 

140 

140 

140 

140 

130 

130 

130 

130

29% 

22% 

15% 

3SOx i 

25% 

25% 

12% 

250/0 

10% 

130 

130

Before dissolving.

Condition.

SA .......

Dr ........

S .........

Dr........

S .........

Dr........

s. ........

Dr........

s .........

Dr........

Dr........

S .........

Dr........

SA .......

Dr........

SA .......

Dr........

{ 8........

,.,.......

^s. .......

| S ........

! "3S. .......

Is ........

rs ........

c S. .......

) <z

(S. .......

,s. .......

<Dr.......

2pX103

130 

80 

130 

80 

130 

80 

140 

80 

140 

80 

140 

80 

140 

80 

130 

90 

130 

90 

320 

120 

120 

120 

120 

120 

120 

120 

130 

130 

130 

130 

130 

80 

80

H

3-25 

2-94 

3-28 

3-07 

3-20 

3-08 

3-93 

3-34 

4-00 

3-48 

4-16 

3-05 

4-3C 

8-54 

3-23 

2-82 

3-25 

2-G1 

2-29 

2-20 

2-27 

2-22 

3-10' 

3-25 

3-13 

3-25 

3-14 

3-21 

3.13 

3-20

2-37 

2-39

TOX103

24-2 

15-7 

i!4-C 

19-5 

23-0

19-5 

28-6 

29'0 

28-0 

35-3 

4-6 

5-8 

29-7 

21-8 

1G-6 

20-7 

1G-7 

15-4 

14-7 

13-6 

14-6 

11-5 

25-3 

24-2 

27-0 

32-G 

24-3 

9-9 

23-6 

1-5 

0-0 

15-4 

1G'8

inirxio»

7-4 

5-3 

7-5 

G-3 

7-0 

6-3 

7-2 

8-7 

7-1 

101 

1-1 

1-9 

G-8 

6-1 

5-1 

7-3 

5-1 

5'9 

G-4 

G-0 

G-4 

5-2 

8-1 

7-4 

8'6 

10-0 

7-7 

3-1 

7-5 

0-5

o-o

6-5 

7-0

No.

C17 

* 18 

(19 

( 20 

C21 

' 22 

C 23 

< 24 

C25 

< 26 

< 27 

* 28 

C20 

< 30 

C 31 

* 32 

C 33 

t 34 

C35 

t 37 

y 30 

t 38 

r 39 

1 40 

41 

I 42 

' 43 

44 

45 

4G 

40ct

J§«

i||48

'Dissolved in a beaker under identical conditions of concentration and temperature.

s. ..........

s. ..........

s ...........

s ...........

130 

130 

130 

130

rS ........

JDr. ......

iDr. ......

130 

80 

130 

80

2-59 

2-58 

2-48 

2-48

18-3 

19-6 

22'9 

17.2

7-1 

7-0 

9-2 

G-9 (

49 

t» 

*

* Dissolved in boiling acid, sp. gr., 1-1.5,30% HCL.

1 Dissolved in cold acid, sp. gr., 1-15,30% HCL.

I Dissolved in dilute cold acid, sp. gr., 1-07,15% HCL.

^ Dissolved down.

|| Drawn down.
44 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

TABLE 10. Graphitic carbon in soft and drawn steel Continued.

[S, annealed from red heat, with very slow cooling (commercial). SA, heated to redness and cooled hi 

air. GH, glass-hard. An, annealed at 500°. Dr. fresh drawn, usually from diameter = 2p = 0-13""

Dissolved under identical conditions in Erlenmeyer flask with Bunsen. valve. Acid 1-13 at 

24°. 60|:C taken per 1 gr. iron.

Before drawing.

Original condition.

r,n. ..........

GH. ..........

(Ht.. .........

GH. ..........

Finn! condition.

«!

s...........

s...........

s. ..........

SA. ........

SA.........

SA .........

SA. ........ 

S ...........

S ...........

s...........

s. ..........

2pX103

130 

130 

130 

130 

130 

130 

130 

130 

130 

130 

80 

80

Before dissolving.

Condition.

s. ........

Dr........

S. ........

Dr........

SA .......

Dr........

SA .......

Dr........

S.........

Dr.....,,..

GH.......

An. 450 ...

2pX103

130 

80 

130 

80 

130 

80 

130 

80 

130 

80 

80 

80

M

3-16 

1-77 

3-19 

2-21 

3-03 

2-51 

3-19 

2-82 

5-77 

5-4G 

4-35 

3-50

WtXlO3

12-5 

8-2 

12-3 

6-9 

11-8 

9-1 

11-3 

6-6 

20-1 

0-3

4-2

.W.X10»

3-9 

4-C 

3-8 

3-1 

3-9 

3-6 

3-5 

2-3 

3-5 

1-1

o-o

1-2

No.

,53 

< 54 

( 55 

( 50 

,57 

< 58 

c 59 

\ CO 

,61 

{ 62 

e 63 

\ 64

DISCUSSION.

20. Inconsistency of the results. To obtain a comprehensive survey 

over this large number of data, it is expedient to lay them down graphically. This can be done clearly by erecting perpendiculars equidistant, on the same base for each of the states S, SA, G-HSA, Dr, 

Dr, SA, etc., and laying off the divers carburation data TO along the 

vertical lines. Points belonging to the halves or other parts of the 

same wire are then connected by a line with an arrow indicating the 

direction of the operation. Thus, S > Dr would denote that one-half 

of the originally soft rod was drawn down, the remainder being left in 

the soft state.

It is well to commence with the rods Fos. 1 to 22, all of these being 

of the same kind of steel (diameter 130cm ). It will be seen that the 

drawn wires here lie within a relatively narrow zone, whereas the soft 

wires are widely scattered. The diagram is such as to suggest very 

pointedly that the operation of drawing steel either precipitates or 

dissolves carbon according as the amount of free carbon in soft steel is 

less or greater than the quantity needful for the drawn state. Fortunately, however, I was induced to suspect an error in these data 

notwithstanding their general consistency and number; for the behavior of the couple Nos. 15 and 16, for instance, is anomalous. I may 

remark in passing that Nos. 7 and 8 showed the marked difference of 

rate of solution already referred to in § 18 Nos. 11,12, and due to the resolution of carbon produced by annealing a thoroughly soft wire in air, etc. 

Nevertheless so remarkable a result was not to be rashly enunciated, 

and I therefore resolved to continue the experiments with steel of
BAKU3.] DISCUSSION OF RESULTS. 45

another kind. Eods 23 to 30 were tested. The results here obtained 

were such as wholly to vitiate the inferences drawn from the first lot. 

At least the drawn samples now lie far apart, and away from the 

earlier drawn group, whereas the soft rods are more nearly identical. 

Hence it began to appear that the data in hand had no discernible 

meaning at all; that the differences of the carburation positions of the 

soft and drawn wire were the result of flaws in the method of chemical 

treatment. These adverse views are substantiated by Nos. 27 and 28, 

which were boiled during solution. The result is a sacrifice of all but 

one-fifth or less of the free carbon found after dissolving in cold acid. 

A few additional experiments, Nos. 31 to 34, made with the first steel 

wire, corroborate the remarks made relative to the deep-seated insufficiency of the method.

21. Errors of the method. Having been obliged to come to these unfavorable conclusions I thought it desirable, in view of the importance 

of the results to be reached, to make some attempt in perfecting the 

method. The experiments 35 to 52 are made chiefly with this end in 

view. The sources of error are unfortunately so complex as to make 

the interpretation a problem of almost insuperable difficulty. There 

are at least six such sources to be considered, viz, temperature; the 

concentration of the solvent acid; the effect of solution in air, and in 

hydrogen; the rate of solution; the variations of structural density of 

the wire, etc.

22. Temperature. Nos. 27 and 28, already given, and Nos. 40 and. 

40a show that at 100° nearly all the free carbon is removed during 

Sblution; and that this is the case moreover for acids of any reasonable 

strength (HOI, 12 % to 25 %). Hence, since the amount of free carbon 

obtained rapidly diminishes (ca3t. par.) with increasing temperature, 

it follows that data for two samples are not comparable unless the 

temperature has remained constant throughout the whole interval of 

solution for each. Particularly does this apply in case of different 

Aveights.

23. Concentration of acid. The strength of acid used is an item of 

even greater importance. This is shown by Nos. 35 to 45. In the first 

group of experiments, Nos. 35 to 38, the effect of concentration in increasing the amount of free carbon is already apparent. Experiments 

39, 40, 41, 42, however, show this more convincingly. In case of concentrated acid (No. 42) nearly all the carbon in steel is precipitated 

during solution. In all such experiments, however, the time of solution is an essential consideration. I do not refer so much to the rate of 

solution as to the time of exposure of the liquid to air or other gases. 

In the present instance, No. 41, which dissolved very slowly in the 

dilute acid, has an exceptionally high position. To some extent the 

same influence may be present in No. 42, which also dissolved very 

slowly under the opposite conditions of very strong acid.

24. Solution in air and in hydrogen, The large differences obtained
46 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

for these two cases are shown in Nos. 43 to 45, and in most of the 

experiments Nos. 49 to 62. The results here obtained are the most 

important of the present section, inasmuch as they indicate the probable nature of the error of the method .and the steps necessary to perfect it. Comparing Nos. 43 and 44, it appears that the solution in 

hydrogen, i. e., in an Erlenmeyer flask provided with a Bunsen valve, 

is accompanied with a precipitation of less than one-half as much 

carbon as separates out under the ordinary conditions of solution in a 

covered beaker. If the acid be very dilute ( 'No. 45) so that solution 

takes a very long time, then the effect of the Bunsen valve is nil, 

because it is not sufficiently tight. It follows from, these data that the 

solution of soft steel is not generally a simple phenomenon; that an 

oxidizable hydrocarbon or similar compound escapes, which in presence 

of air or available oxygen deposits carbon by secondary decomposition. 

This inference is conclusively substantiated by the beaker series, Nos. 

49 to 52, as compared with the flask series (Buusen valve), Nos. 53 

to 56, When solution takes place in a covered beaker, the carbon 

precipitate, besides being in larger amount, is different in character 

from the flask precipitate. The latter is heavy and graphitic; the 

former contain as very light suspended admixture, which it is difficult 

to wash down in the Gooch crucible.

25. Rate of solution. Whether the rate of solution has any direct 

influence on the carbon deposited, I am unable to affirm with certainty. 

If it does, the effect is probably small; for instance, solution in concentrated HC1 (No. 42) takes place relatively slowly, as does also solution m 

dilute acid (41). But the large amount of carbon found is probably due 

to atmospheric influence. Nevertheless, in view of the large thermal 

effect already pointed out, it can not be asserted that the rate of solution is a negligible factor.

26. Structural density. In experiments Nos. 47 and 48 one sample 

was drawn down and the other diminished in diameter by solution, 

whereupon both were identically dissolved for analysis. There is no 

difference in^free carbon discernible. Inasmuch, however, as the drawn 

strain is characterized by superficial condensation accompanied by core 

dilatation, I was induced to ascribe the differences in the values of m 

for rods Nos. 57 to 62 to some such cause; for here the experiments 

were made in a way to take advantage of all refinements of research. 

Yet the low value of No. 62 (corroborated) defies explanation. Had the 

precipitate been too large it might have been ascribable to an imperfect valve.

27. Summary. Summarizing the above, I conclude that such carburation differences as appear in the above data are to be looked upon as the 

result of secondary decomposition. In the case of soft steel the solution in HC1 produces an unstable carbide which, under the influence of 

an oxidizing agency, splits up with a deposition of carbon. The precipitate found in such cases is no indication at all of the carbon actually
METHODS REVIEWED. 47

free in steel. So far as the above results go, the effect of mechanical 

strain on the carburation of steel is not demonstrable; at least all 

molecular disintegration superinduced by mechanical means is negligible in comparison with the present errors of the method for estimating 

free carbon. It might be inferred that the qualitative difference in 

the carburations of glass-hard and of soft steel is also to be suspected. 

In this case, however, sharp distinction may be made as follows: In 

glass-hard steel it is impossible by any rational method of treatment 

to obtain precipitation of free carbon out of the solution. In soft steel 

it is equally impossible by the same rational method of treatment to 

dissolve without a free-carbon deposit. For intermediate tempers 

proportionate amounts are deposited (cf. Nos. 63 and 64, which close 

the analyses).

Finally, to distinguish between the different kinds of carburation 

empirically, two methods suggest themselves: Solution may be made 

either in a current of hydrogen in hermetically-closed vessels, under 

identical conditions of concentration grammes HC1, per gramme Avater, 

per gramme steel), and of temperature, etc., for all wires; or else in a 

current of oxygen under the same identical conditions. In the former 

case presumably only the free carbon in the steel is actually deposited. 

In the latter case (oxidation) the free carbon is definitely incremented 

by the deposition obtained from the oxidizable unstable carbide.

I took steps toward testing the first of these methods (solution in a 

current of hydrogen), but have thus far been prevented from pushing 

the question decisively to an issue.

28. Osmond's a and ft iron. If the difference between steel hardened 

mechanically and the same steel soft is due to Osmond's a and ft iron 

(cf. § 5), then the possibility of molecular change due to the mechanical 

treatment is beyond the province of the present method. It is well to 

bear this in mind. Carbon under certain conditions may be favorable 

to the stability of ft iron, but it is not essential to its existence beyond 

a certain relative quantity. In view of these considerations the experiments of the next chapter are more pertinent to the subject of inquiry.
CHAPTEE IY.

THE EFFECT OF STRAIN ON THE RATE OF SOLUTION OF STEEL.

INTRODUCTORY.

29. The difficulties encountered in the preceding section, in which 

the effect of strain on carburation is directly put to test, suggested a 

possible solution by indirect methods. It is well known that the effect 

of mechanical treatment, for instance, of rolling, drawing, etc., is apt to 

show itself in the structure of the metal when acted on by acids. The 

fiber of iron may thus be clearly exhibited; and even in cases of galvanic solution the surface often becomes furrowed and marked in a 

way indicative of definite structure. It appears, therefore, that some 

parts of the metal are more electropositive than others; audit does 

not seem improbable that homogeneous and strained metal may be 

distinguished by studying their respective rates of solution under 

given conditions.

METHOD.

30. Solution experiments of this kind are given in the following 

tables. The method of experiment is again simple. The weighed rods 

of known length are placed in a small tray made of narrow strips of 

hard rubber. Thus they can all be submerged or withdrawn from the 

acid at the same time. Some care was necessary as regards drying 

the samples before weighing. Having taken them out of the solution 

on the tray (this was $p shaped, with the wires placed across either 

set of parallel bars or rubber strips are placed edge upward), the wires 

were submerged in water and then dried in an air bath at 100°. The 

bars of the tray were notched so as to avoid displacement of the wires. 

As they could be carried together, it was not necessary to touch them 

except with the forceps before weighing. This structure of the tray, 

moreover, is such as to allow free circulation of acid. The essential 

data to be noted are the temperatures of the acid and the weight and 

length of each rod before and after dipping. From this the radius for 

each case may be calculated. Two series of experiments must be made 

for each group of steel rods. It is first: necessary to find the consecutive solution data in case of homogeneous wire gradually decreasing in 

thickness; with these data the corresponding results for wire drawn 

doivn from the original homogeneous wire may then be compared.
BABUS.] DATA FOR SOLUTION OF STEELS. 4U

TABLES.

31. In Table 11 I give the results for three identical, nearly homogeneous steel wires, about 5cm long and originally '127cm thick, submerged 

in dilute acid of a given kind, for consecutive intervals of time of one 

hour each. Here o is the temperature of the acid; m the muss of the 

rod in grammes, r the radius, and Ar the consecutive decrement of 

radius due to solutioi i. The progress of the experim ent may be followed 

by consulting either M or r. Corrections are applied for the reduction 

of length due to solution.

In Table 12 data are given for drawn steel, the thickness of the 

individual wires varying between 127cm and -084CI ". They are all 

drawn down-from the same sample of soft steel, so that the larger 

thicknesses are soft, the thinner wires very resilient and brittle. All 

wires, Nos. 1 to 7, are submerged together; but variations of strength of 

acid, time, and temperature are the causes of differences of mass dissolved in successive solutions. From Table 11, however, the rates of 

solution for different thicknesses of homogeneous Avire are known. 

Hence the behavior of the drawn wires during each solution can be 

tested. In Table 12, Jf', r', Ar 1 denote the mass, radius, and variation 

of radius of the drawn wire, Ar' being simply the difference between 

consecutive values of r before and after solution. Ar may therefore 

be interpolated from Table 11 by making the first term of Ar1 and Ar 

identical. The wires of each group are submerged and withdrawn, 

in like manner. In passing from group to group, however, a change 

of acid is unavoidable.

TABLK 11. Solution of soft (8} steel, normal experiment.

[Time, lh . i=5c'". 8 = 7-7].

e

JfXlO1 

rXlO3 

ArXlO3

32-4

495

63-8

0

32-3

4G4

61-0

1-9

82-3

4 26

59-3

2-6

32'0

389 

56-6

2-7

e

JfXlO3 

rXlO3 

ArXlO'

32-4

490

64-0

0

32-3

466

C2-0

2-0

32-3

427

59-4

2-6

32-0

390 

56'7

2-7

6 

JtfXW3 

rXlO3 

ArXlO'

32-4

497

64-0

0

33-3

467

62-1

1-9

32-:?

428

59-4

2-7 

32-0

391 

50-8

2-0

1 0 ' JUX10" 

rX10:l 

ArXlO3

31-0

351

53-8

2-8

32-5

314

50'8

3-0

i 32-5

280

1 48-0

2-8

33-0

243 

44-8

3-2

0 

MXW 

/ XKP 

ArXlO3

31-0

354

54'0

2-7

32-5

316

51-0

3-0

32-5

281

48-1

2-9

33'0

244 

44-9

3-2

0 

JlfXlO3 

rXlO3 

ArXlO3

31-6

355

54-2

2-6

32-5

317

51-1

3-1

32-5

282

48-2

2-Q

33-0

,245 

45-0

3-2

0 

JlfXlO3 

rXlO^ 

ArXlO3

33-3

207

41-3

3-5

33-3

171

37-6 

3-7

32-8

137

33-7

3'9

31-5

in

30-2

3-5

0 

MX 103 

rXlO3 

ArX10:l

33-3

209

41-5

3-4

33-3

174

38-0

3-5

32-8

140

34-1

3-9

31-5

114 

30-C

3-5

e

JfXlO1 

rXlO3 

ArXlO3

33'3

211

41-7 '

3-3

33-3

175

38-1

3-6

32-8 :

142

34-3

3'8

31-5

115 

30-8

3-5

e ifxio3

rXlO" 

ArXlO'1

31-5

90

27-2

3'0

31-7

65

23-1

4-1

32-0

41

18-3

4-8 

32-0

21 

13-1

5'2

e MXW* 

rXlO1 

ArXlO"

31-5

93

27-7

2-9

31-7

68

23-6

4-1

32'0

43

18-8

4-8

32'0

23 

13-7

5-1

0 

Jl/X10:l 

rXlO3 

ArXlO3

31-5

93

27-7

3-1

31-7

68

23

4-1

32-0

44

19'0

4-6

32-0

23 

13-7

5-3

Bull,
50 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

TABLE 12. Solution of drawn steel, originally S.

[Z = 4-5«'». J=7-7.]

IPX 10' 

r'XlO" 

Ar'XlO3 

ArXlO1

No. 1.

441

63-5

411

61-4

2-1

2-1

384

59-3

2-1

2-1

367

58-0

1-3

1-3

337

55-4

2-6

2-6

313

53-4

2'0

2-0

286

51'2

2-2

2-2

238

40-7

4-5

4-5

197

42-5

4-2

4-2

130

34-5

. 8-0

8-0

98

30-0

4-5

4-5

 67

24'8

5'2

5-2

M'XW3 

r'XlO" 

Ar'XlO1 

ArXlO3

No. 2.

413

61-5

376

58-6

2-9

2-2

348

56-4

2-2

2-1

325

54-5

1-9

1-3

292

51-7

2-8

2-7

264

49-1

2-6

2-1

237

46-6

2-5

2'3

185

41-2

5-4

4-8

144

36-5

4-7

4-6

84

27-8

8-7

8-9

56

22-7

5-1

5-1

25

15-4

7 - 3

6-8

Jlf'XlO3 

r'XlO1' 

Ar'XlO3 

ArXlO'

No. 3.

359

57-3

324

54-3

3-0

2-3

288

51-4

2-9

2-2

264

49-1

2-3

1-4

229

45-8

3-3

2-9

198

42-6

3-2

2-3

170

39-5

3-1

2-5

113

32'1

7-4

5-9

90

28-7

3-4

5-3

38

18-6

10-9

10-3

12

10-5

8-1

6'5

Jlf'XlO3 

r'X10:t 

Ar'xlO3 

ArXlO'

No. 4.

309

53-2

267

49-5

3-7

2-3

233

40-2

3-3

2-4

204

43-4

2-8

1-5

166

39-1

4-3

3-2

136

35-4

3-7

2-5

109

31-7

3-7

2-8

69

25-2

6-5

6-0

41

19-5

5-7

6-3

2

4-7

2-8

Jlf'XlO3 

r'XlO* 

Ar'XlO3 

ArXlO3

No. 5.

248

47-5

218

44-7

2-8

2.5

184

41-1

3-6

2-5

155

37-7

3-4

1-6

119

33-0

4-7

3-5

94

28-9

4-1

2-8

63

23-9

5-0

3-3

31

16-7

7-2

7-2

6

7-5

9.2

M1 X103 

r'XlO3 

Ar'XlO3 

ArXlO3

No. 6.

203

43-3

176

40-3

3-0

2-7

148

36-7

3-6

2-7

117

32-7

4-0

1-7

79

26-9

5-8

3-7

53

22-1

3-9

3-1

24

15-0

71

3-8

Jf'XlO1 

r'XlO» 

Ar'XlO1 

ArXlO3

No. 7.

193

42-0

167

39-2

8-8

2-7

137

35-5

3-7

2-7

106

31-1

4-4

1-8

66

24-6

6-5

4-0

37

.18-5

6-1

3-3

13

10-9

7-6

(4-3)
BARUS.] SOLUTION OF SOFT STEEL. 51

Tables 13,14,15 and 16 are constructed on the same plan as Tables 

11 and 12. The steel wires, however, are of different temper. Table 3 

contains the normal experiments, the rods being submerged in hydrochloric acid of a given strength throughout during successive intervals 

of two hours each. The rods are about 5cm long, and ISTos. 1, 2, 3 are 

annealed at red heat in air from the soft state; Nos. 4, 5, 6, annealed at 

red hea.t in air from the glass-hard state; No. 7 is glass-hard. 6, M, r, 

etc., have the signification already given. In Table 14 five soft rods, 

annealed at red heat in air, are tested. M', r', Ar' are their solution 

data. Ar is interpolated from Table 13 by making the first term of 

Ar and Ar' identical. In Table 15 six glass-hard roda-, annealed at red 

heat in air; are tested. Notation as before. Abbreviations which refer 

to temper and hardness are given in § 19 above.

TABLE 13. Solution of soft (S A) steel, normal experiment.

[J. 5C». (5 = 7-7.]

e

M rXlO1 

ArXlO''.

No. 1.

 489

63-5

32-4

 455

61-2

2-3

32-4

 415

58-5

2-7

28-7

 387

50-5

2-0

29-4

 358

54-3

2-2

29-3

 328

52'0

2-3

S-SA.

e 

M rXlO3 

ArXlO1 .

No. 2.

 487

63-4

32-4

 452

Cl-1

2-3

32-4

 412

58-3

2-8

28'7

 383

56-2

2-1

29-4

 354

54-0

2'2

29-3

 325

51-8

2-2

29-5

 296

49-5

2-3

e

H rXlO3 

ArXlO1 .

No. 3.

 486

63-2

32-4

 452

61-1

2'1

32-4

 413

58-3

2-8

28'7

 385

5C-3

2-0

29-4

 356

54-1

2-2

29-3

 327

52-0

2-1

29-5

 299

50-3

1-7

0 

M rXlO1 

ArXlO1 .

No. 4.

 492

03'7

32-4

 401

61-7

2-0

32-4

 425

59'3

2-4

28-7

 398

57-2

2-1

29-4

 372

55-4

1-8

29-3

 345

53'4

2-0

29'5

 318

51-3

2-1

G H-S A.

9 

M rXlO3 

ArXlO1 .

No. 5:

 495

C3-8

32-4

 462

61-7

2-1

32-4

 425

59-3

2-4

28-7

 396

57-2

2-1

29-4

 369

55-1

2-1

29-3

 341

53-0

2'1

29'5

 313

50-8

2-2

e

M rX103 

ArXlO3 .

No. 6.

 491

63-5

32'4

 401

61-7

1-8

32-4

 426

59-3

2-4

28-7

 400

57-5

1-8

29-4

 374

55-5

2-0

29'3

 348

53'0

1-9

29-5

 320

51-4

2-2.

Gil.

e

M 

rX.10'' 

ArXlO : .

No. 7.

 489

63-5

32-4

 407

02-1

1-4

32-4

 441

60-3

1-8

28-7

 423

59-1

1-2

29 '4

 404

57-0

1-5

29-3

 381

56-2

1-4

29'5

 363

54.8

1-4
52 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

TABLE 13. Solution of soft (8 A) steel, normal°experimcnt Continued. 

[Z=5<"». 4=7-7.]

S-SA.

e

M rXlO3 

ArXW.

No. 1.

N

e

M7'XIO*

ArXlO3

No. 2.

29'5

 271

47-3

2-2

30-0

 241

44-7

2-0

 30-0

 213

41-8

2-9

30-0

 188

39-4

2-4

30-0

 170

37-5

1-9

31-5

 146

34-7

2-8

29-0

 124

31-9

2-8

28-3

 107

29'6

2-3

27-6

.089

27-0

2'6

27-0

 073

24-5

2'5

g

M. 

rXlO3 

ArXlO3.

No. 3.

29-5

 276

47-7

2-6

30-0

 245

45-0

2-7

30-0

 218

 42-4

2-6

30-0

 193

39-9

2-5

30-0

 174

37-9

o2'0

31-5

 152

35-5

2-4

29-0

 129

33-1

2-4

28-3

 112

30-5

2-6

27-6

 094

27'8

2-7

27-0

 078

25-4

2-4

G H-S A.

g

M rXlO3 

ArXlO3 .

No. 4.

29'5

 293

49-2

2-1

BO-0

 269

47-0

2'2

30-0

 241

44-5

2-5

30-0

 218

42-4

2-1

30-0

 200

40-7

1-7

31-5

 177

38-2

2-5

29-0

 156

35-9

2-3

28-3

 138

33-7

2-2

27'6

 120

31-5

2-2

27-0

 101

29-2

2-3

g

M rXlO3 

ArXlO3 .

No. 5.

29-5

 287

48'7

2-1

30'0

 261

46-4

2-3

30-0

 233

43-7

2-7

30-0

 208

41-4

2-3

30-0

 189

. 39-5

1-9

31-5

 164

36-7

2-8

29'0

 144

34-4

2-3

28-3

 124

32-0

2-4

27-6

 106

29-5

2-5

27'0

 089

27-1

2-4

g 

ir rXlO3 

ArXlO3 .

No. 6.

29-5

 297

49-6

1-8

30-0

 273

47.5

2-1

30-0

 247

45-1

2-4

30-0

 223

42-9

2-2

30-0

 205

41-2

1-7

31-5

 183

38'9

2-3

29-0

 162

36-6

2'3

28-3

 144

34-6

2-0

27-6

 127

32-3

2-3 

27-0

 110

30-1

2-2

GH.

0 

M rX10s 

ArXlO1 .

No, 7.

29-5

 345

53-3

1-5

30-0

 326

51-9

1-4

30-0

 306

50-2

1-7

30-0

 287

48-6

1-6

30-0

 271

47-3

1-3

31-5

 250

45-4

19

29-0

 232

43-8

1-6

28'3

 217

42-3

1-5

27-6

 202

40-8

1-5

27-0

 187

39-2

1-6
BAKUS.] SOLUTION OF STRAINED STEEL. 53

TABLE 14. Solution of drawn steel, originally S, changed to SA. 

[1=4. o . 6=7. 7.]

M' 

r'XlO3 

Ar'XlO3 

ArXlO3

No.l.

 390

63-4

 381.

62-7

0'7

0-7

 372

Cl-9

0-8

0-8

 368

61-3

0-5

0-5

 359

C0.8

0-5

0'5

f352

60-3

0-5

0-5

 346

59-8

0-5

0-5

 330

58-4

1-4

1-4

 332

56-9

1-6

1-5

 277

53-4

3-5

3-5

 2G4

52-0

1-4

1-4

W r'XlO3 

Ar'XlO3 

ArXlO3

No. 2.

 340

59-1

 329

58-2

0-9

0-7

 321

57-5

0-7

0'8

 310

57-0

0-5

0-5

 307

56-3

0-7

0-5

 301

55-7

0-6

0-5

' 293

54-9

0-8

0-5

 271

52-8

2-1

1-4

 259

51-6

1-2

1-6

 223

47.9

3-7

3-6

 206

46-2

1-7

1-4

Jf r'XlO3 

Ar'XlO3 

ArXlO1

No. 3.

 264

52-1

 251

50-8

1.3

0'7

 242

50'0

0-8

0'8

 235

49-2

0-8

0-5

 225

48'2

1.0

0'5

 215

47.2

1-0

0.5

 205

46-0

1-2

0.6

 183

43'3

2-7

1-5

 162

41-3

2-0

1-6

 129

36.5

4.8

3-8

 110

33-7

2-8

1-6

M' 

r'XlO3 

Ar'XlO3 

ArXlO3

No. 4.

 212

46-8

 201

45-6

1-2

0-8 -

 188

44-3

1-3

0'9

 180

43-1

1-2

0-6

 169

41-8

1-3

0-6

 159

40-7

1.1

0-6

 148

39-1,

1-6

O'G

' 124

35-8

3-3

1-0

 102

32-8

3-0

1-7

 066

26-1

6.7

4-1

 048

22-5

3-6

1-7

Jf' 

r'XlO3 

Ar'XlO3 

ArXlO3

No. 5.

 167

41-5

 153

39-8

1-7

0-8

 143

38-5

1-3

0-9

 134

37-1

1-4

0-6

 121

35-3

1-8

0-6

 107

33-4

1-9

0-6

 094

31-2

2-2

0-6

 068

26-6

4-0

1-7

 047

22-3

4-3

1-8

 014

11.8

10-5
54 THE MECHANISM OP SOLID VISCOSITY. [BULL. 94,

TABLE 14. Solution of drawn steel, originally S, changed to SA Continued. 

[1-4. 0« . <J=7.7.]

M1 

r'XlO3 

Ar'XlO3 

ArXlO3

No.l.

 246

50-4

1-6

1-6

 230

48-7

1-7

 1-7

 214

46-9

1-8

1-8

 199

45-3

]-6

1-C

 176

42-6

2-7

2-7

 143

38-5

4-1

4-1

 129

36-5

2'0

2-0

IP r'XlO3 

Ar'XlO3 

ArXlO3

No. 2.

 188

44.1-

2.1

1-7

 171

42-2

1-9

1-8

 150

40'2

2-0

1-9

 140

38'1

2-1

1-C

 117

34-6

3-5

2-8

 086

29-8

4-8

4.3

 072

 27-3

2-5

2-1

M' 

r'XlO3 

Ar'XlO'5 

ArXlO3

No. 3.

 093

31-1

2-6

1-8

 075

27-9

3.2

1-9

 058

25-0

2-9

2.1

 043

2.1-4

3.6

1-8

.026

16-5

4-9

M1 

r'xlO3 

Ar'XlO' 

ArX103

No. 4.

 031

18-0

4-5

1-9

 016

13-3

4-7

M' 

r'XlO3 

Ar'XlO3

No. 5.
BAUDS.] SOLUTION OF STRAINED STEEL.

15. Solution of drawn steel, originally G-H, changed to SA.

[Z=3-S< to (i=7-7.1

if'

r' X 103 

A r' X 103 

A r X 10'

No. 1.

.OQ'J

63-8

 382

G2-8 

1-0

1-0

 375

62-1

0-7

0-7

 371

Cl-8

0-3

0'3

 303

61-1

0-7

0-7

 35G

CO- 5

0-6

O'G

 350

GO-1

0-4

0-4

 329

58-3

1-8

1.8

 311

5G-7

1-6

1-0

 277

53-4

3-3

3-3

 261

51-9

1-5

1-5

1 If' r' X 103 

A r' X 10' 

A r X 103

No. 2.

 '(91

59-0

 311

58-7 

I.Q

1-0

 305

57-4

1-3

0-7

 303

57-3

0-1

0-3

 294

5G-5

0-8

0-7

 288

55-9

0-G

0-6

 282

55-2

0-7

0-4

 200

53-1

2-1 1

1-8

 244

51-4

1-7

1-7

 214

48-3

3'1

3'4

 199

46-5

1-8

1-5

M'

7" X 103

Ar' X 10' 

A r X 10''

No. 3.'

 272

54-3

 201

53-2 

1-1

1-1

 254

52-4

0-8

0'7

 219

52-0

0-4

0-3

 242

51-2

0'8

0-7

 235

50-5

0-7

0-6

 229

49-9

o-c

0-4

 207

47-5

2-4

1-9

 188

45-3

2-2

1-8

 156

41-2

4-1

3-0

 138

38'7

2-5

1-6

MI 

» ' X 103 

A r' X 103 

A r X 103

No. 4.

 229

49' 9

 217

48-5 

1-4

1-1

 209

47'8

0-7

0-7

 204

47-2

o-o

0-3

 195

46-0

1-2

0-7

 187

45-1

0-9

0-7

 180

44-2

0-9

0-5

 156

41-1

3-1

9 2-0

 13G

38-4

2-7

1-8

 102

33'3

5-1

3-7

 081

29-6

3-7

1-7

M1 

r' X 10' 

A r' X 10' 

A r X 10'

No. 5.

.ion

 170

43 '7 

1-9

1-2

 168

42-9

0-8

0-8

 104

42-3

0-6

0-3

 154

40-9

1-4

0-8

 148

40-1

0-8

0-7

 139

38-8

1-3

0-5

 116

*35-3

3-5

2-0

 090

32-2

3-1

1-9

 055

25-4

G-8

4-0

 038

21-3

4-1

1-8

M' 

r' X 10s 

A r' X 10s 

A r X 103

No. 6.

 151

40'5

 143

39-8

0'7

0'8

 139

39-4

0-3

0-3

 137

38-G

0-8

0-8

 120

37'0

1-0

0-7

 119

36-0

1-0

0-5

 094

32-1

3-9

2-0

 072

28-0

4-1

2-7

 027

18-3

9-7

4-0

 014

12-7

5-G
THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

TABLE 15. Solution of draton steel, originally G-H, changed to SA. Continued,

[Z=3'8«" to 4-0"". 8=7-7.)

M' 

r'XlO3 

Ar'XlO3 

ArXlO1

No. 1.

 244

50-1

1-8

1-8

 229

48-6

1-5

1-5

 213

46-9

1-7

1:7 

 197

45-1

1-8

1-8

 174

42-4

2-7

2-7

 140

38-1

4-3

4-3

Jf r'XlO3 

Ar'XlO1 

ArXlO1

No. 2,

 183

44'6

1-9

1-9

 167

42-5

2-1

1-6

 150

40-3

2-2

1-8

 136

38-5

1-8

1-8

 114

35-2

3-3

2-8

 085

30-3

4'9

4-5

Jf r'XlO3 

Ar'XlO3 

ArXlO3

No. 3.

 121

36-5

2-2

2-0

 105

33-7 

2-8

1-7

 090

31'4

2'3

1-9

 074

28-5

2-9

2-0

 053

24-0

4-5

3-0

 028

18.8

5-2

Jf r'XlO3 

Ar'XlO3 

ArXlO*

No. 4.

 065

27-4

2-2

2-1

 049

23-3

4-1

18

 034

19-4

3-9

2-0

 021

15-4

4-0

M' 

r'XlO1 

Ar'X.103 

ArXlO3

No. 5.

 021

16'7

4'6

 008

11-8

4-9

M' 

r'XlO3 

Ar'XlO3 

ArXlO'

No. 6.

*
SOLUTION OF TEMPERED STEEL.

Finally, iu table 16, solution comparisons are made between glasshard and soft wires, in the way indicated for the preceding tables. 

Hods ISTos* 1 and 2 are glass-hard; Nos. 3 and 4 soft; IsTos. 5 and 6 

annealed at low red heat in air; N"o. 7 annealed at very high red heat 

in air. The time of submergence was 3 hours.

TABLE 16. Solution of 'steel, G-H, S, SA.

[{=5"". A=7'7.]

an*

No. 1.

JI/'XIO3 

rXlO1 

ArXlO3

487

63-4-

4 S3

03-1

0-3

477

62-7

0-4

 400

02-2

0'5

402

01-7

0-5

455

0.1-2

U-5

418

CO-8

0-4

442

60-4

0-4

436 

60-0 

0-4

So. 2.

JU'XIO" 

rXW 

ArXlO1

201

40-7

199

40-5

0-2

190

40-2

0-3

193

39-9

0-3

189

39-4

0-5

180

39-2

0-2

183

38-8

0-4

180

38-5

0-3

177 

38-2 

0-3

S.

No. 3.

jlfXlO' 

rXlO3 

ArXlO'

489

C3-5

445

Gl-2

2-3

387

57-7

3-5

324

53-3

4-4

259

48-2

5-1

201

42-8

5-4

140

36-9

5-9

102

31-0

5-9

No. 4.

JfXIOS 

rXlO3 

ArXlO3

205

41-1

189

39-8

1-3

167

37-8

2-0

144

35-4

2-4

120

32-6

2-8

99

29-8

2-8

78

26-8

3-0

61

23-8

3-0

45 

20-5 

3-3

S-SA.

No. 5.

JlfXlO3 

rXlO3 

ArXlO'1

487

63-4

477

02-7

0-7

465

621

0-6

453

61-4

0-7

439

60-4

1-0

424

59-4

1-0

412

58-6

0-8

400

. 57-8

0-8

 387 

57-0 

0-8

No. 0.

JIXIO3 

rXlO3 

ArXlO3

199

40-5

195

40-1

0-4

191

39-8

0-3

186

39-3

0-5

181

38-7

0-6

176

38-3

0-4

170

37-7

o-o

165

37-1

0-6

161 

36-7 

0-4

SA.

No. 7.

.MX lO3 

rX10» 

ArXlO3

487

63-4

e

481 | 28

63-0

0-4

475

62-5

0-5

469

62-2

0-3

462

01-7

0-5

455

61-2

0-5

447

60-7

0-5

442

60-4

0-3

435 

59-8 

0-6

28

' DISCUSSION.

32. Incidental errors. I may state at the outset that secondary 

errors, such, for instance, as might be ascribed to passivity of steel, are 

largely avoided. Care was taken to rub the rod with platinum, at the 

beginning of each solution. Nevertheless, it is not impossible, when 

the rods were left to dry over night, at the close of a day's series of experiments, that some retardation during the first stages of solution on
58 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94

the succeeding day may be appreciable. A serious difficulty is encountered because of the unavoidable change of the room temperature 

during the successive solutions. In some instances I endeavored 

partially to avoid this by making the solution in the cellar underneath 

the laboratory. But even here the temperature is insufficiently constant for fine work.

33. Effect of surface. As regards the plan of treating the above 

results, it appears probable that the masses dissolved in case of a given 

sample and given solvent, must be simply a function of radius and 

time (correction being made, of course, for loss at the ends). If the 

rate of solution be denoted by p, its A^ilue at the radius r must be

where d is the density of the sample and dt the elementary time of solution. p therefore is the mass dissolved under the given condition of 

form and solvents per unit of surface, per unit of time. Thus it appears 

that the mean rate during the time t will be

(fpfdt)/tOT-(fi/t)/fdr,

each taken between corresponding limits. In other words the mean 

rate

where t.2 ti=t. If therefore t be chosen constant, rates of solution are

to each other as *

p'__?V r/. ~p ~>a ~-^n

It is, therefore, an apparently simple problem to deduce the relative 

mean rate directly from the differences of radii time, figure, and chemical conditions remaining the same. But from the data of the above tables 

such simple relations do not at all appear. Indeed the correspondingdifferences of mass dissolved are very much more nearly constant than 

the corresponding differences of radii. In other words, in the case of 

cylindrical figures of small radius, the mass dissolved is nearly independent of radius; i. e., independent of the surface exposed to the action 

of acid. The conditions are such that fixed masses of solid are transferred by solution to the liquid state, and in proportion as radius 

diminishes the thickness of shell dissolved in given times rapidly increases.

34. Effect of diffusion. Without doubt the underlying cause of this 

observation is a diffusion phenomenon. For instance, let c be the concentration at the surface of separation of solid and liquid, the radius 

being r. Then c.Znrcir is the amount of salt dissolved in the first 

liquid shell. Now, when this salt dissolved is transferred by diffusion 

to a distance r1 (r'>r), the concentration c' is necessarily smaller, for 

c.27rrdr=c/27rr'dr', or cr=c'r'. It follows at once that the difference of 

concentration for a given value of dr increases at a rapid rate when the 

radius approaches zero. On the other hand the rate of transference
BAHUS.] DIGEST OF SOLUTION DATA. 59

of the solid material into tlie liquid state must depend on the rapidity 

with whic'h c diminishes in the direction of r. Hence the rate of solution will increase in proportion as smaller thicknesses of wire are encountered, inasmuch as the conditions favorable for the transportation of the dissolved metal are enhanced. This follows more rigorously 

from Tick's law. Adapting Fourier's theory of heat conduction to 

questions involving diffusion, Fick1 proposed dc/dt=nd2c/d!X?, where 

c is the concentration and K the diffusion constant. In other words, 

the time rate at Avhich concentration progresses is proportional to the 

space rate of increase of the same quality. The truth of this fundamental assumption was afterwards rigorously tested by H. F. Weber.2 

Fick's equation, when dc/dt=0, or the diffusion has become stationary, 

referred to polar coordinates is d2 (rc)/dr'*=0. Since c=0 for r= o>, 

this reduces to cr=cV.

The diffusion effect will necessarily be of smaller consequence Avhen 

solution. takes place at very low rates ; for instance, in the case of glasshard steel. It is also greatly modified, past recognition, perhaps, by 

the escape of gases from the body undergoing solution. In this way 

convective currents are set up accompanied-by distributive effects very 

much more rapid than the diffusion phenomenon. A further disturbance is gravitational convection.

35. Wires originally soft. Nevertheless, in discussing the above 

results, it is advisable to consider the relative consecutive value of4M 

for given comparable conditions of solution, quite as much as the relative values of Ar, or the consecutive rates. Inasmuch as there is a 

striking tendency toward constant values of AM independent of r, 

when r lies below a critical value, apparent in all my results, it is 

probable that a law characteristic of the solution of filimentary or 

small bodies is here expressed.

Turning first to Table 11, the following correlative values of r=(r2 + 

TI)$; p=r2 'TI and AM=M2 Mi are apparent. The variable pis identical with the rate, since the times and chemical conditions of solution 

are constant.

TABLE 17. Digest for originally soft wires.

r X10S .............

pXlO' .............

AMX10' ..........

03

2-0

30

01

2-0

39

58

2-7

37

55

2-7

37

5?,

3-0

37

49

35

40

3'?,

37

43

3-4

35

40

3-0-

30

30

3-9

33

32

3-5

27

 >ft

3-0

0(.

4-1

25

01

4-7

24

10

?1

The salient property of these data is the rapid increase of rate encountered immediately after the superficial layer is dissolved off. 

After this AM is nearly constant between r .060 cm and r = .040 cm, 

whereupon it decreases rapidly. On the other hand p increases continually and at an accelerated rate. Irregularities of outline are doubtless

1 Fick: Pogg. Ann., xciv, p. 59, 1855; Phil. Mag. (4), x, p. 30, 1855.

s H.T. Wober: Phil. Mag. (5), viii, p. 523, 1879; Wied. Ann., vii, p. 469, 536, 1879.
60 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94

the effect of temperature. The distortion is greatest in the curve for 

4M. With these data the. seven drawn rods of Table 12 are to be compared. As before 2r' r \ + r '2 and p' = r'2 r 'i for each solution, and 

Table 11 furnishes values of p in case of the normal rod, for every 

value of r'. By making the first term, of each series identical a 

corresponding series of Ar = pi$ obtained. It is expedient to represent p and p' graphically as functions of r'. If this be done it appears that after the first shell is dissolved, the solution of drawn wire 

takes place at greater rates than the solution of homogeneous wire of 

the same radius. After dissolving seven shells the results show irregularities, easily accounted for inasmuch as the finer rods gradually become of irregular shape and fissured. . Again the results for AM may 

be represented as a fuuction of r', showing values, which as a rule, increase as r' decreases. From these data as a whole it follows that drawi i 

steel is cset. par. more easily soluble than homogeneous steel ; again 

after the superficial layers are removed the rate of solution increases 

with the intensity of drawn strain or resilient properties of the wire.

36. Wires annealed. Turning now to the results of Table 3, in which 

the normal data for wires softened in air and for a glass-hard wire are 

inserted, it is clear in the first place that as soon as the superficial 

layers are removed the rate of solution increases. This result corrobo- 

. rates Table 11. Apart from this, however, the variations of rate of 

solution aud of the other data are here of a much smaller order than 

was the case for Table 11. AM decreases with radius at a somewhat 

more rapid rate than before, and hence p 1 = Ar' now increases at a 

decidedly less rapid rate than in Table 11. This is shown in the following summary for wires softened in air (i. e., S-SA and GrH-SA).

TABLE 18. Digest for wires annealed in air.

W Xr=.....

103 X p' = ....

103 X A M-..

62

2-1

33

60

2-6

38

58

2-0

27

56

2-1

27

54

2-1

28

52

2-1

29

50

2-2

19

46

2-4

27

44

2-6

28

42

2-3

24

40

1-8

18

38

2-5

23

35

2-4

22

33

2-3

17

30

2-4

17

28

2-4

17

It is also shown in the results for the glass-hard wire (G. H.), identically submerged.

TABLE 19. Digest for hard wires.

103 X » = .....

103 xp = .....

103 A M= ....

63

1-4

28

61

1-8

26

60

1-2

18

58

1-5

19

57

1-4

20 -

55

1-4

21

54

1-5

18

53

1-4

19

51

1-7

20

49

1-6

19

48

1-3

16

46

1-9

21

45

1-6

18

43

1-5

14

41

1-5

16

40

1-6

15

With these data the values of tables 14 and 15 are to be compared 

in a way already enunciated in case of tables 11 and 12. The data being constructed graphically, it again follows, almost without exception, 

that both in tables 14 and 15 the rates of solution of drawn wires are 

greater than the similarly circumstanced rates for homogeneous wires.
BABUS.] INFERENCES FROM SOLUTION DATA. 61

There also is a weight of evidence in favor of the result that solution 

increases with the degree of resilience, i. e., the intensity of the drawn 

strain. In other words, rate of solution increases as the (drawn) diameter of the wire of each group diminishes, supposing as above that the 

superficial layers of the wire have been removed. Finally, in Table 14, 

AM also continually increases from larger to smaller diameters, for 

each group, until the diameter of the rod has been considerably reduced. In Table 15, however, this result is not so pronounced, and 

AM remains nearly constant.

Summarizing the above results as a whole, it follows that the rate of 

solution of drawn steel is greater than the rate of the same homogeneous metal similarly circumstanced. After the superficial layers (probably dense low-carbon steel) have been removed, the ra,te of solution 

increases with the intensity of drawn strain. To a smaller and less 

definite extent this is true also of the masses dissolved in equal times, 

in cases of resilience of different intensities, other things remaining the 

same.

37. Relation to Drowne's inferences. Table 16 finally has been drawn 

up to show the enormous difference of rate of solution between glasshard and soft steels. Submergence being identical for all rods, it is 

curious in the first place to note the difference of rate of Nos. 3 and 4, 

both being very soft steel, as well as the high rates of solution of these 

two rods as compared with the others. The special feature of these 

experiments is the fact that rods annealed at red heat in air dissolve quite as slowly as rods quenched glass hard; and this is particularly the case when the rods are annealed at high-red heat, No. 7. 

This observation calls to mind the inference of Dr. Drowne 1, viz, that 

" there is a limited range of temperature probably near the point of 

solidification of the metal, within which the separation of carbon from 

iron takes place, and that the amount of carbon separated in any given 

instance is proportional to the time consumed by the pig iron in passing through the limited range of temperature." Now, as the rate of 

solution increases directly with the free carbon in steel, caet. par., the 

present data substantiate Dr. Drowne's reasoning.

38. /Summary, Perusing the above pages as a whole, they furnish 

evidence favoring the opinion that the effect of strain on metallic structure is a reconstruction of the metallic molecule; but since the rate of 

solution of the drawn metal is greater, it does not follow that the re- 

 suits so obtained are due to the presence of ft iron in a iron, unless it 

be supposed that the negative character of the former relative to the 

positive quality of a iron increases the rate of solution by local electric action. The corrugated and deeply fissured appearance of the 

rods after the radius has been much reduced is in keeping with this 

view. Indeed, an exceedingly curious action, which I frequently observed, may be mentioned. It often happens that the solution at the

1 T. M. Drowno: Traus. Am. Insfc. Mining Bug., HI, 1874-'75, p. 41.
62 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

ends of the rod, instead of rounding off the corners, eats its way decidedly into the axis, so as to form a reentrant cone of some depth. 

Again, if there be periodic distributions of density from the surface inward, an inference which, from earlier observations 1 with glass-hard 

rods does not seein improbable, the regularity of solution experiments 

would be disturbed.

>Cf. Bull. U. S. Geol. Survey, No. 35, p. 38,1886.
GHAPTEE V.

THE HYDROELECTRIC EFFECT OF CHANGES OF MOLECULAR

CONFIGURATION.

INTRODUCTORY.

39. The hydroelectric method is usually regarded as the most delicate 

criterion for testing changes of molecular constitution in metals. Unfortunately its indications are, in the present instance, distorted by 

polarization. Polarization, moreover, is apt to be much larger than the 

effect to be studied, so that the observer is obliged to resort to methods 

of measurement in which a fair degree of constancy of the error in question may be assured. From this it follows that unless the hydroelectric 

forces are as large as the interval " glass hard" to u soft," the effect of 

strains which can not be applied'without removing the wire or metal 

from the hydroelectric bath is not observable. For in such a case the 

polarization varies with each immersion. ' Moreover, certain strains, 

like the drawn strain, show different mechanical conditions at different 

distances from the axis. Hence the hydroelectric constant of such a 

rod, were it obtainable, would be a complex magnitude.

In magnetization, the hydroelectric effect of which has been discovered by Kemseu1 and studied by Mchols2, and more recently by 

Eowland and Bell3, small hydroelectric effects (<.03 volts) can be detected because the metal during straining remains in place. Among 

other mechanical strains, traction, and perhaps torsion, admits of similar 

application to a metallic wire in place.

APPARATUS.

40. Tn the annexed figure 4 I have shown the apparatus used, aac 

and bb are consecutive pieces of a given kind of soft wire. Of these aa 

is to be stretched, bb examined in the homogeneous state. Hence aa 

is fixed between two points, of which the lower is on the circumference 

of an iron drum, D, which can be rotated by aid of the lever LL and 

frictionally fixed in position after any rotation. Usually the arcs of 

rotation of D were 180°, and four or five such strains could be applied 

to the wire consecutivelyJ^efore rupture ensued.

1 Rein sen: Am. Chemical Journal, nr, p. 157, 1881.

2 !Nichols: Am. Jour. Sci., xxxi, p. 272, 188(3: ibid., xxxv, p. 290, 1S37.

8 Eowland npd Jtell: PJiil. Mag. (5), xxvi, p. 105, 1888.

63
64 THE MECHANISM OF SOLID VISCOSITY. I BULL. 94.

Before and after each of these strains measurements of hydroelectric 

state were made. For this purpose both wires are surrounded by glass 

tubes AA and BB respectively, held together by aid of the little block 

of wood C. These tubes were closed below with rubber corks through 

which the wires passed without leakage. The tubes were filled either 

with a concentrated solution of zinc sulphate, or with distilled water, 

or other material which does not act strongly on the metal. The electrolytic connection between A A and BB 

is made by a siphon, S, filled with the 

liquid of the tubes and closed at s with 

a parchment septum. The upper ends 

of the wires b and c were in connection 

with the terminals of a Mascart electrometer, or with the properly adjusted 

wires of an apparatus for a zero method. 

After straining the wire aac to the 

point of breakage, the apparatus was 

reversed and bb now strained in the same 

manner. In this way the number of 

distinct measurements for each adjustment could be doubled.

The wire being 54crn long and the 

diameter of the drum about 1.7cm the 

extension of wire per rotation of 180° 

was approximately 2.6cni , or <?_L/.L=.05 

nearly; The amount differed slightly 

when wires of different thicknesses were 

used. The reduction of diameter of iron 

wire before and after straining to breakage is therefore considerable.

EXPERIMENTS.

41. Zero method. In communicating 

my results I will omit the data obtained 

galvanically by the zero method. For 

the polarization disturbances are here 

of larger order than in electrometric 

work, an annoyance which vitiates the 

greater delicacy of measurement. The 

remark, however, is not superfluous that all the results were found to 

corroborate the electrometric data.

42. Results for iron. The hydroelectric effect of traction is characterized by a temporary and a more or less permanent part. The temporary part may be given by observing the differences of potential at 

the end of each minute after straining, as well as the throw of the needle

a

r 

*

-^ 5

N

-«4

^

r<

v~"

\

s

;

s

^ C:

^ \

^ \ 

> s,

\ 

\ 

\ 

s, \ \ ' <.

3/ ?r

toeLectrarr

Jjtoecath

,

\B

t

I

FIG. 4. Apparatus for measuring the hydroelective effect of stretching.
BARC8.] 'HYDROELECTRIC EFFECT OF STRETCHING. 65

immediately after. The difference of potential which remained when 

the temporary effect had subsided I called the permanent part. An 

allowance of five minutes was usually regarded sufficient. Of course 

this assumption is arbitrary; but whatever errors are committed are of 

like effect throughout the series. The value of the throw is expressed 

in volts, as are the other data. In all I made about 7 series of this kind, 

two of which are given in Table 20. The diameter of the iron wires before straining was 2p,=-080cm j after breaking 2pA =-078cm ,

TABLK 20. Hydroelectric effect of tensile strain. 

IEOX WIRE.

Strain.

0- 

I 

 II 

III 

IV

0

I 

II

I LI 

IV

eXIO3 temporary.

Throw.

 34 

 0

+ 8

-26 

 0 

+10 

+12

lm 2- a 4m

i

1

eXIO3 

permanent.

+ 9 

+ 7 

+11 

+14

+ o

 14 

 13 

- 8 

 4 

 1

Strain.

o'

I

i II 

III 

IV

0

I 

II 

III

IV

eXIO' temporary.

Throw.

 18 

 2 

+ 5 

+10

 15 

 0 

+ 2 

+ 5

1- 2 1 " 3 4m

eX 

per 

net

4 

-f

4 

-f

-t

-f4

Extension, dJr/i=-05 per pull.

Radial contraction, fy> /p < -03 per pull. *

Mean permanent potential increase == + "003 volts per pull.

The character of the data of table 20 is such as to indicate superimposed permanent and temporary effects. The former is distinctly 

electropositive in all my results; negative differences of potential are 

numerically decreased, positive differences increased. The increase of 

electropositive quality takes place simultaneously with the increase of 

length, at a rate which varies somewhat in the different experiments, but 

the mean value of which is about .003 volts per pull of the extension 

6L/L = 0'05. This is equivalent to a decrease of the wetted external 

surface of the wire of about 5 per cent, provided there be no change of 

volume. The measured value is less than this, for the circumference 

before straining was found by aid of the micrometer to be 27tpB =. 27cm 

and after straining 2nph = .24cm as an aggregate of four pulls. This 

corresponds to less than 3 per cent of diminution of the wetted surface 

per pull.

The temporary effect is equally definite in character. Independently 

of the value of the permanent effect, the former is at first invariably 

negative, which quality is successively reduced, until finally the value, 

having passed through zero, becomes positive. The intensity of the first 

negative throw is strong; as a rule more so than the final positive thro\v. 

Bull. 94- 5
66 THE MECHANISM OF SOLID VISCOSITY. [HUM,. 94.

DISCUSSION OF RESULTS.

43. Having thus obtained some knowledge of these phenomena for 

iron, it is expedient to indicate in passing some reasons for their probable cause. Iron submerged in any aqueous solution is polarized positively by a coat of hydrogen. Hence it is practically a condenser, whose 

capacity increases directly with the wetted surface, caeteris paribus. The 

effect of strain is therefore of a twofold kind : In consequence of the jarriug and vibration which unavoidably accompany the stretching, some of 

the hydrogen is mechanically shaken off, and the positive potential or 

positive polarization decreased to a lower limit. Hence the negative 

throw after the h'rst strain. Simultaneously with this result the capacity 

of the wire is diminished in consequence of stretching. Hence the positive potential or positive polarization is increased. If this last effect 

gradually predominates over the other (effect of jarring), the temporary 

throw changes from negative to positive.

This explanation is nearest at hand, and it need not be sufficient; but 

it is clear at once that before any hydroelectric effect can be ascribed 

to strain as sucli, it is necessary, to evaluate the polarization effect, as 

well as other minor errors, such for instance as are due to the increase 

of temperature of the wire during stretching. (Of. Wiedemann's "Elektricitat," vol. n, p. 773, etc.)

DATA FOR DIVERS METALS.

44. In the following tables I have inserted data corresponding to 

Table 20, but obtained with German silver, brass, copper, iron, all the 

wires being of larger diameter than before. The notation is the same as 

above. In Tables 21 to 24 zinc sulphate in concentrated solution is the 

electrolyte; in Tables 25 to 27 distilled water is used. At the ends of 

tables, the mean values per pull of extension ($L/L), radial contraction 

(dp/p), permanent potential increase e volts, are inserted for each wire.

TABLE 21. Hydroelectric effect of tensile strain. »

German silver, zinc sulphate. ' ~

Strain.

0 

I

II

III

IV

0 

I 

II 

III 

IV 

V

cXlO3 tenipor

Throw.

..........

4-36

+42

+50

+69

+ 32

lm

32

16

19

42

13

........

=

2'"

12

6

 1

18

7

........

u-y.

3"'

13

_ 4

 10

9

4

410

16

 .19

 ]8

2

A

ex 10* 

permanent.

+27

+28

+35

+47

+51

+24 

+30 

+26 

+24 

+23 

+18

tL/L Extension per pull = .05. 

It;iili:il contraction per pull = .02. 

Mean permanent potential increase per pall = .005.
BAUUS.] HYDROELECTRIC EFFECT OK STRETCHING. 67

TABLE 22. Hydroelectric effect of tensile strain. 

Brass, zinc sulphate, \$. II -157 '

Strain.

0 

I

II

III 

IV

0 

I

II

eXIO' temporary.

Throw.

+21

+41

+48

+17

18

1»

18

31

30

4

10

2m

12

28

20

2

C

3'°

12

25

18

0

3

4,n

13

24

15

 2

1

eXIO3 

permanent.

+23 

+39

+ 09

+C5

 15 

 18

 18

fL L Extension per pull . '05. 

Jliulinl contraction per pull = '015. 

Moan permanent potential increase per pull -- '015.

TAIJLE 23. Hydroelectric effect of temtile strain.

Copprr, zinc, sulphate, 2,7°* ~ .{^(jcm'

Strain.

0 

I 

II 

III 

IV

0

u1}

$

eXIO3 temj)orary.

Tlirow.

0 

0 

+3

+2

+2 

2

1-

0 

0 

2 

2

2

2

2>"

0 

0 

1

2

2

3"

0 

0 

2

2

4'"

0 

0

2

ex 10s 

permanent.

+4 

+0 

+0 

-1-6

 6 

+0 

 1

Extension per pull = - 05.

Kndinl contraction per pull = '025.

Mean permanent potential increase per pull = -001.

TABLE 24. Hydroelectric effect of tensile strain. 

Iron, zinc sulphate, ' = .' '

Strain.

0 

I

II

III

IV

0

I

II

III 

IV

eXIO' temporary.

Tlirow.

 58

 36

 22

 36

 52

 30

- 30

lm

 42

 24

 3

 24

-38

-17

-18

2-

_ 29

 12

 2

 17

 24

 10

 6

3"'

 22

_ j

 2

 34

 18

 G

 4

4 m

 17

 5

 1

 10

 15

 4

 0

eXIO3 

permanent.

+8 

 6

 5

 3

 7

+4 

_ 1

 7

 7

Extension per pull = -05.

liailial contraction per pull = -015.

Mean poruiauent potential increase per pull = -033.
68 THE MECHANISM OF SOLID VISCOSITY. 

TABLE 25. Hydroelectric effect of stretching.

2 P ' 166 cm2 p h = -154 "».

[BULL. 91.

0

I

11

III

IV

0

I

II

III

IV

e X 103 , temporary.

Throw.

+82

+58

+63

+62

+42

+21

+28

+29

1"

73

40

49

44

42

14

21

24

2m

59

22

28

27

42

13

11

14

3">

48

8

14

14

38

8

 1

 7

4m

39

 2

7

8

36

6

0

3

C X 103,

ent.

 76

 44

 52

- 56

 60

+ 73

+103

+ 91

+ 77

+ 67

Extension per pull = -05

Radial contraction per pull = '02

Mean permanent potential increase per pull = ± -015

TABLE 26. Hydroelectric effect of stretching.

Strain.

0 

I 

II 

III 

IV

0 

I 

II 

III

IV

eX 103, temporary.

Throw.

-17 

 10

-33 

- 4 

 6

1-

+46 

+24

 17

+ 7 

+13

Qiu

60

28

- 6

+14 

+14

3m

67 

29

 3

4m

70

 1

-

e X 103, 

permanent.

+16 

-+79 

+95

-56 

-40 

 23 

 6

Extension per pull = -05

Radial contraction per pull

Moan pennanent potential increase per pull = + -027

TABLE 27. Miscellaneous work, 

Copper wire, water.

Strain.

0. .............

I, II. .........

111,1V .......

eXIO3, temporary.

Throw. 1-

.................

 42

3

K

+29 

+13

+ 2

+28 

+ 9

2-

+29

+ 7

3m

+34 

+ 8

4m

eXIO3, 

permanent.

+15 

+ 4 

+ 2 

+27 

+28

Extension per pull = -05 

Radial contraction per pull = -03 

Potential increase per pull = -015
BABOS.] HYDROELECTRIC EFFECT OF STRETCHING. 69

TABLE 27. Miscellaneous work Continued. 

Brass wire, water.

Strain.

0.... ..........

Jerk..........

Kiib ..........

Kub. .........

Rub. .........

0...... ........

I .............

exlO1, temporary.

Throw.

01

35

17

+35

lm

35

2,n

35

3.=

31

4 

31

ex-101 , 

permanent.

- 8 

_ 25

 21 

 10 

 6 

 9 

 0 

+25

Iron wire, water.

0.. ............

Jerk.......... 42

 49

 45

15

28

O1

0

 0

7

+ 2

+ 1

 40

39

 30

 30

 18

German silver, 2p=-080cm . Zinc sulphate.

Strain.

0............

I ...........

n. .........

m. ........

eXlO1, permanent.

4-13 '

+ 7

+ n

0

Strain.

0............

I ...........

II ..........

m.........

e X 10'1, penua- 

 iienl.

 1

 0

 0

6

EFFECTS CLASSIFIED.

45. Turning first to the permanent hydroelectric effect of traction, 

Tables 21 and 22 show increments of decidedly larger positive value 

than hold for iron in Table 20. The effect for copper in Table 23 is 

nearly zero, and for iron, Table 24, actually negative. Whatever the 

effect may be it is necessarily to be considered doubly specific, depending both on the metal and the liquid. Hence I made further investigations in Tables 25, 26, 27, by replacing zinc sulphate solution by distilled water. Here it is found that the permanent effect is decidedly 

less In magnitude for zinc sulphate than for water, from which a close 

relation of these phenomena and of polarization may be inferred. Moreover, the effect in case of water is by no means as regular as in the other 

case. In Table 25, for instance, the permanent points inclose an area of 

rhomboidal outline, showingthattheeffects of initial pulls arc different in 

sign from those of final pulls. Again, copper, which in case of zinc sulphate is not charged by traction, shows a hydroelectric effect in case
70 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

of water comparable with that of other metals. Again the changes 

iron- water are excessively large. Irrespective of sign, the magnitude 

of the hydroelectric effect has increased with the diameter of the wires 

used.

Among results bearing on a later paragraph (§46) I may mention that 

the permanent effect of traction of iron in zinc-sulphate is sometimes 

positive and sometimes negative, depending on the qualities of the 

wire. Table 27 shows a specimen of German silver in which the permanent effect is negative.

I have given the temporary effects in their absolute values (increments) 

at consecutive times, independent of the potential of the wire. In case 

of German silver, of brass, of copper, these effects are distinctly positive, i. e., opposite in sign from the temporary effects for iron, which are 

invariably electro-negative both in the present instances (Tables 24, 20) 

and in Table 20.

DISCUSSION OF ERRORS.

46. Returning to the explanation suggested above (§ 43), it appears that 

in German silver, copper, and brass the effect of diminished capacity 

and of exposure of fresh surface, 1 due to stretching, both of which are 

positive, predominates over the negative effect of accidental jerking. 

In iron they do not so predominate. It is specially to be noticed that 

the permanent effect is entirely independent of the temporary effect. 

Inasmuch as the permanent effect is obtained by commutation (each 

electrode being alternately put to earth) the residuum of the temporary 

effect is discharged. From this it may be conjectured that the apparatus acts like a double condenser.

In Table 27 I give some data bearing on the probability of this explanation. The wires were adjusted in the usual way, but instead of 

being stretched they were only jerked by the action of the machine. In 

this case a negative temporary effect is obtained in all the metals, about 

of the same numerical order as the data of the earlier tables. Similar 

results follow after rubbing immersed parts of the wires.

Again, the temporary effect may be due to frictiou at the axle of the 

drum. But such an effect would discharge itself to earth, unless the 

wire and water act as a condenser. It would necessarily fall out of 

the permanent effect, for here the wires are alternately put to earth.

47. Variable capacity. If the wire be of the form of a cylinder of 

length I and radius r, its capacity is approximately

C=l/2ln~. i r

Hence, since the charges are constant

Q = VC = V'C' or V( F'=log rj log r' 

whence it follows that (TV and V being identical)

_

log T-^log r

iy_ ' (

'This being at once acted on by tho liquid, falls under the considerations made in 

the text.
BAttUS.} HYDROELECTRIC EFFECT OF STRETCHING. 71

From this expression the polarization of the wire may be calculated 

from the difference of potential produced by traction. The data of 

Tables 20 to 27 then furnish the following values of V'. The subscripts 

attached to the symbols for metals refer to the number of the table.

TABLE 28. Digest.

Metal.

log r/log r/r' . 

AFXIO 1 ......

7,' ...........

Fo,

26 

3X4

_I-'31

Arg2

20 

5X4

+ 52

Bl'3

33 

15X4

+1-98

Zn SO.,

Cu4

19 

1X4

+ 08

Pe6

32 

-3X4

- 38

Br0

25

4-1 ^ V4.

±1-50

Pe7

30 

27X4

+3'24

H20

Cu8

?0 

15X4

 fl-14

If the wire with its surrounding liquid acts like a condenser, of which 

the layer of polarizing gas (hydrogen) is the medium through which induction takes place, then the capacity is that of two concentric cylinders 

of radii r2 and r,, respectively, and the common length /. Here

C= ^ , r~ , j or C = ~~ ( 1+f^r X nearly, when r2 TI = e and K, the

specific inductive capacity of the layer of gas is taken as 1. Now, if AVO 

proceed as above, and consider the charge constant, an equation similar 

to (1) may be obtained by introducing some reasonable postulate relative to the thickness e of the polarizing gas. Suppose e = constant; i. e., 

that before and after each pull the layer has not changed in thickness. 

Then Vj V'=(2r'+e) / (2r+c), or, approximately (IV and V being identical),

V2/=~i^'(V V) ....... (2)

Again, suppose the mass of gas to remain the same, so that 2?tre = 

27rr'e'. Then 7/F'=(2r/2 +er) / (2r2 +e), or, approximately (V;/ and V 

identical),

Hence, Tables 1 to 8 furnish the following digest:

TABLE 29. Digest.

Metal.

r/(r' r) iv - - 

r?/(r «_r*) F>l .......

To,

r39

( -12 

>75

( -22

Arg.2

42

 21

77

 38

Br3

71

1-06 

130

2 '04

Zn S04

Cu4

38

 04

72

 07

Pc6

07

- 20 

127

- 38

BrB

51

±'76 

100

±1-50

Fo7

57

1-54 

110

3'00

B V 0

Cu8

38

 57

72

1-08

In discriminating1 between Fi, F2 , F3, it is clear that the conditions

'Tho close analogy of .1 polarized voltameter and a doubled condenser was pointed ont by Varley 

(Pliil. '1'rans., vol. cxu, p. 129, 1872) an.l others. The subject is minutely discussed in Wiudcinanii's 

Eloktricitiit, vol. n, pp. 758 to 771. It may bo observed that in equation (2) the increment of potential 

varies as the decrement of the wetted surface.
72 THE MECHANISM OF SOLID VISCOSITY. [Bm.t.94.

under which. Vr applies are not given, and that the maximum probability 

rests with F2 ; but this quantity is not decidedly above the order of possible polarization for the cases under consideration. Hence, the permanent hydroelectric effect due to a change of the electro-positive quality 

of a metal by traction, is obscured beyond recognition by the unavoidable variations of polarization accompanying the experiment.

SINGLE WIRES.

48. Having thus failed to obtain reliable evidence from the hydroelectric experiments, I endeavored with some pains to discern a direct 

electrical effect (potential) due to the traction of an insulated wire. 

Here again I failed; for not only is the needle of Mascart's electrometer always in motion when connected with a train of insulted wire, 

but the effect of traction is friction at the points of fastening at the ends 

of the wire. This friction of the metal wire against the insulators is apt 

to evoke relatively powerful charges as compared with the true effect 

of traction. Particularly is this the case if during traction the distended 

wire begins to loosen. By soldering loops at the ends of the wire the 

frictioual disturbance can be reduced to a minimum, without, however, 

furnishing' definite evidence of a purely traction effect.

SUMMARY.

49. In the above paragraphs I have endeavored to refer the very 

definite hydroelectric results obtained to the simplest explanation at 

hand. But it is necessary to bear in mind that the phenomena are so 

largely beyond the observer's control that an exhaustive experimental 

discussion is out of the question. It would be unwise, therefore, to 

lose sight of other points of view from which they may have a direct 

bearing on the real question in hand, viz., the possibility of molecular 

change in a metal corresponding to each change of strain imparted to 

it. The question is steadily gaining in probability. Osmond, after 

making an elaborate pyrometric study of the conditions under which 

Gore's phenomenon occurs in iron, postulates the existence of an a and 

a ft variety of iron. These varieties when cold may be distinguished 

physically by their difference in hardness. Moreover, /?-iron, besides 

being produced spontaneously out of a-iron, above a certain temperature in red heat, may also be produced in small quantity by strainings-iron at ordinary temperatures. I pointed out that such a hypothesis 

involves the occurrence of a and /? varieties of most metals, even when 

no such criterion as is given by Gore's phenomenon is observable. 

Quite recently Mr. Carus-Wilson, 1 from experiments made on the viscosity of strained steel, summarizes his experience in favor of Osmond's 2

view. Unfortunately, the well known effects of strain on the therino-

___________________________j_____________

1 Carus-Wilson, Mature, vol. 41, 1893, p. 213.

2 Osmoucl, Annales des Mines, July-August, 1888; M6m. Ae I'artillcrie cle la Marino, Paris, 1838, p. 4.
lunus.] HYDEOELECTRIC EFFECT OF STRETCHING. 73

electric quality and on the resistance of metals are not at once interpretable, except,'perhaps, in so far as they are accompanied by hysteresis ((John, Warburg, Ewing, Schumann). The ion theories of metallic 

electrical conduction now coining into vogue (J. J. Thomson, Gicse:i ), 

conditioned as they must be by the occurrence of marked molecular 

instability in metals, are steps in the same direction. 1 will therefore 

merely point out, in concluding, that the simple explanations given 

above for the temporary effect, which was found consistently negative 

at first in iron, and consistently positive in all the other metals, is not 

satisfactory. It is permissible to regard it as the direct result of a 

change of molecule due to straining;, for it is precisely in the first stages 

of the temporary effect that evidence for such molecular change may 

reasonably be sought.4

1 (liesc, Wied. Aim. vol. 37, 1889, p. 576.

2 Cf. Rowland ami Boll (loo. cit.), who are obliged to base their inferences on the temporary hydroelectric effect of magnetization. In all problems of this'character it is necessary to distinguish between the, positional stability and the chemical stability of a molecule. It does not follow that if (In; 

former quality is increased the latter will also he, for a chemical solvent, does not pick up molecules 

bodily, but by disinte»Tatin,Li; them. In certain experiments on the isothermal electromotive force of 

aDaniell between 10 and 1,800 atmospheres, 1 will indicate this further.
CHAPTEB VI.

THE SECULAR ANNEALING OF COLD HARD STEEL. 

INTRODUCTORY.

Inasmuch as the method I used for testing Maxwell's theory of the 

viscosity of solids contains a proof of that theory a fortiori, I did not 

distinguish in that paperl between a break-up of configurations of molecular wholes and the more intensified break-up in which the integrity 

of the molecule itself is invaded. The experimental distinction is not 

always easy. If, for instance, I dissolve certain solids (pitch, say, in 

turpentine) I may produce a continuous series of viscous fluids; but 

the molecular mechanism by which this is brought about can not in 

the present state of our knowledge of solution be said to be known. I 

may cite another striking example, ebonite, which above 100° loses 

vicosity at an exceedingly rapid rate by mere heating; but, again, the 

molecular change which produces the viscous effect is obscure. And 

so generally in less remarkable experiments.2 In the case of metals, 

it appears that those elements whose molecules are least stable and 

possibly mouatomic 3 (K, Na, etc.) are of a soapy consistency, so that 

here vicosity (Nachwirkung) and permanent set can hardly be distinguished. In general it appears that metallic permanent set is physical manifestation of looseness of molecular structure. If, as in the case 

of annealing glass-hard steel, the rigid arch (say) of molecular wholes 

breaks up because one or more of the molecules, the stones of that 

arch, disintegrate, and if the decomposition be of a kind that the debris 

may be chemically recognized, then, by coordinating the viscous and 

the chemical observations, I obtain a fairly good notion of the molecular 

mechanism which has produced the viscous effect. This is the method 

I applied to prove Maxwell's theory. But partial disintegration or 

reconstruction of molecules may easily be conceived to occur in such a 

way as to escape detection altogether or at least to escape detection 

as much as does a break-up of configurations of molecular wholes. It 

may, I think, be reasonably supposed that the solid molecule is of the 

form M,,, in which n is variable; and any given value of n will occur

'Philosophical Magazine, London, August, 1888.

2 Of. Lothar Meyer (Die modernen Theorien der Cheniie, Breslau, 1884, chapter vin,) on solid molecular structure.

3 Ibid, chapter XVI, sec. 308, etc. 

U
HAHus.1 SECULAR ANNEALING OF HARD STEEL. 75

$ frequently according as it is proportionately greater or less than 

the mean or typical value of n for the solid. The effect of strain, of 

change of strain, or even of long continued secular subsidence is merely 

to vary the distribution of molecules M,t , so that the general properties 

of any observably finite part of the solid do not change. 1

I will adduce other points of view in succeeding papers; but the suggestions stated are sufficient, I think, to show the importance of discerning whether the cause of viscous deformation in tempered steel is the

type of viscous deformation in general or whether, in using the pile-

's n:)m?na of annealing steel to test Maxwell's theory, I have merely interpreted the exception to prove the rule. The result of such an investigation, besides throwing light on the structure of solid matter, must

ultimately lead to inferences bear ing directly on the questions of fusion,

. solution, and volatilization.

"RESULTS FOR HOMOGENEITY OF RODS.

51. This inquiry, being essentially a comparison of detail, will consume 

much time before it can be brought to an issue; and, as the individual 

parts of my work have led to results which are of interest 2 apart from 

the purposes to which I hope ultimately to apply them, it is perhaps 

best to communicate the data separately. The following results on the 

secular annealing of cold glass-hard steel essentially sustain the inferen ces of my last paper. They were omitted because of the space occupied by the discussions there given. The rods to which the data refer are 

of Stubbs's best steel, tempered in a special apparatus, 1 by aid of which 

the wire heated to redness electrically is suddenly whipped into water. 

Freshly quenched samples of wire showed specific resistances (0° C.) as 

high as s=48. All the rods were tested for longitudinal uniformity of 

temper by stepping off, as it were, the resistance of lengths of 2cm. each 

for each of the consecutive 3cm. of wire. The total length being about 

25cm ., eight measurements were thus made. A device utilizing Matthiessen and Hockin's method, and provided with a suitable rider, 

enabled me to do this with reasonable accuracy. Table 30 contains 

the results as obtained with three batches of wire, of the diameters

1 In other words, it is here supposed that the assumption of solid state has not thoroughly eliminated 

the liquid or oven the gaseous molecule and that it has, on the other hand, produced molecules of 

an ultra-solid complexity. Here I touch the keynote of certain difficulties in my mind against conceiving the solid molecule as a uniformly distinct whole, capable of rotation (Kohlrausch viscosity) 

or capable of trail. slat i 011 from strained to iaotropic configuration (Maxwell viscosity). I look upon it 

as a more cumbersome thing, which may under favorable conditions even lose its identity, and whioh, 

when undergoing the motions stated, comes into serious conflict with contiguous molecules. Such a 

view, even if it be mere surmise (excepting the case of hard steel discussed), is a suggestive working 

hypothesis; for it seems broad enough to enable me to circumscribe the true phenomenon by clipping 

the postulate. This is the general endeavor of my present work.

8 It is well known that experiments on the secular changes of metals are being made at Glasgow by 

Mr. Bottomloy. Cf. Brit. Assoc. Report, 1888, p. 537.

3 Bull. U. S. Geol. Survey, No. 14, 1885, p. 29. My present apparatus is horizontal in form and enables 

'me to quench the wires from any degree of red heat in water or other liquid at any desirable temperature. See Fig. 5, p. 7, Bull. No. 73, 1891.
76 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

2/>=-081cm ., -044cm., and 127cm ., respectively. The approximate resistance (microhms) of the 2cm . of length is designated by r.

TAKLK 30. Longitudinal uniformity of I CM per of the t>teel rods. Variation from mean, 

in. terms of the electrical interval, liard-soft.

No. 1.

r=18500.

 002

4

2

 1

 C

4

1

- 4

No. 11.

r=rC1200.

 007

.- 2

 7

 10

1

1

1

10

No. 2.

18500.

 002

 2

 2

No. 3.

17700.

 000

0

5

2 i 5

 2 5

_ 0

 2

 13

0

1.0 - 4

No. 12.

00603.

 007

 1

 4

 7

4

_ ^

4

13

No. 13.

61200.

 003

 3

 3

 10

5

 3

8

8

No. 4.

17600.

 003

 2

 2

7

 2

 6

 2

 3

No. 5.

17700.

 010

10

 7

 2

6

 7

 11

2

No. 14. .NV 15.

69200. ' O'JOOO.

 023 ! -016

_ 1 _ i

1 3

 7

 4

 9

2

 4 ' 12

 4 1

_ 4 8

No. C.

18500.

 005

- 3

 7

5

1

 2

 7

9

No. 16.

6800.

 000

 2

3

 2

 2

 2

3

7

No. 7.

18400.

 004

1

1

7

7

 5

 8

 5

No. 17.

No. 8.

18500.

 009

 11

 11

5

 3

5

5

1

No. 18.

6700. j 6583.

 OJ1

1

5

 3

 3

1

_ 3

1

 -Oi)9

7

15

ti

 1

11

 5

 20

No. 9.

17400.

 032

18

11

 46

 64

 16

23

41

No. 19.

7290.

 001

1

10

10

11

- 11

No. 10.

17900.

 006

 6

2

2

 2

 6

10

 6

No. 2J.

6S50.

 -OK!

 20

4

17

13

13

 11 13

 11 4

With the exception of No. 9, the variations are, as a rule, well within 

1 per cent, of the electrical value of the interval hard-soft. Where 

the resistance is larger or smaller than the mean value, it is possible 

thatthe parts were accidentally splashed by the water immediately before 

quenching or quenched at a different degree of red heat. But, inasmuch as the series of measurements for each rod takes some time and 

as the effective resistances are necessarily small, I believe that the rods 

are even more homogeneous than Table I indicates; for the errors introduced by variations of temperature, by the difficulty of clamping the 

thin, very brittle rods (soldering would change the temper enormously), 

and by other inconveniences of manipulation, are by no means negligible. Hence the degree of homogeneity found may be considered quite 

satisfactory.

MASS CONSTANTS OF BODS.

52. In Table 311 give the mass w, length i, and density at 0° C., z/0, of 

some of the rods. The latter datum is essential for the determination 

of the sections. I shall also use it in the future in determining the secular volume-changes of these wires. R<ids ISTos. 11 to 15 are too thin for 

direct measurement. Hence a mean value of /*0 was here assumed. I 

may add that in the soft state the deivsity of these rods is about /70 = 

7-80.
BAUUS.] SECULAR ANNEALING OP HARD STEEL.

TABLE 31. Mass constants of the glass-hard steel rods, June, 1S85.

77

No.

1

2

3

4

5

6

7

8

9

10

vn

9-

 9910

 9544

 9970

1-0483

1-0079

1-0243

1-0089

1-0074

1-0666

1-0293

I

centim.

24-95

24-02

25-25

26-30

25-46

25-80

25-47

25-50

26-68

25-58

Ao

g/cm3 .

7-710

7-689

7-703

7-705

7-703

7-687

7-670

7-682

7-726

7-719

No.

11

12

13

14

15

16

17

18

19

20

m

a-

 3257

 3322

 3170

. -2888

 3004

2-4713

2-4857

2-1043

2-5327

2-3557

I

centim.

27-94

28-30

27-20

24-35

2G-07

25-63

25-70

22-50

26-00

24-40

4o

fir/cm3 .

7-076

7-671

7-544

7-085

7'<553

53. Electrical constants of rods. Table 32 contains the-electrica,! constants of these rods; rt being the observed resistance per centimeter 

at *°, a the temperature coefficient, and SQ the corresponding specific 

resistance at 0° 0. The wires were quenched on June 1 and 2,1885, 

and the measurements made at the time given, only a few days after 

hardening. Sections and radius are given under q and p respectively. 

In most cases q is individually determined.

TABLE 32. Specific resistance of. the glass-hard steel rods, measured Jiine 4 and 8, 1885.

[Effective length, 20 cm. to 26 cm.]

No.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

1C

17

18

19

20

gXlO6

Centim.3

5152

5168

5126

5173

5139

5165

5164

5143

5174

5214

1520

1520

1520

1520

1520

12560

12610

12400

12650

12620

2pX103

Centim.

 80-6

44

. 120-5

rt

Microhm.

9260

9250

8870

8810

8840

9260

9200

9260

8720

. 8950

' 30670

30320

30620

30080

30990

' 3400

3382

4144

3643

3427

t

°0.

27-5

27-8

28*3

27-0

27-2

26-8

27-0

26-3

26-3

25-1

25-2

25-3

24-8

25-5

'26-8

26-4

20-4

26-6

20-7

27-2

aXlO3

1-5

1-5

.1-6

1-6

1-6

1-5

1-5

1-5

1-5

1-5

1-5

1-6

1-5

1-6

1-5

1-7

1-7

1-5

1-6

1-7

«o

Microhm.

46-0

46-0

43-7

43-8

43-7

46-1

45-8

46-0

43-6

45-1

45-1

44-4

45-0

44-1

45-4

41-0

41-0

49-5

44-3

41-5

Finally, Table 33 contains the electrical constants of these rods made 

about thirty-seven mouths after the first incusurement. It also con-
78 THE MECHANISM OF SOLID VISCOSITY. [DULL. 9i.

tains the variations, Jr,, of the resistance per centimeter, as well as the 

variations, As0 , of the specific resistance. It will be seen that ds0 is 

negative throughout, whereas the effect of atmospheric influence and 

the unavoidable abrasion in cleaning the surfaces of the wires before 

measurement would produce a positive error. The same bridge and 

the same standards of German silver are used both in the measurements of Table 32 and of Table 33. The fact that the wires differ in 

diameter, and therefore vary largely in resistance, is a guarantee against 

the effect of differences of sectional errors of the bridge wire. Again, 

although zteo is essentially the difference of secular change between the 

steel-wire and the German-silver standards, the fact that two standards 

(1-0 ohm and (M, respectively) were used at least partially eliminates 

the error due to variations in the standards. Moreover, the electrical 

effects of corresponding variations of temper (steel) and of the drawn 

strain which the German silver may possibly carry are enormously different. For instance, if glass-hard steel is boiled long enough the 

change of resistance may reach 12 per cent and more. The effect of 

boiling German silver is of the order of some tenths per cent. 1 Hence I 

apprehend no serious error in ascribing the whole of the observed variation of s0 in Table 33 to secular annealing of the glass-hard steel rods 

under experiment.

TABLE 33. Specific resistance of the glass-hard steel rods measured July 9, 1888, and the

secular variation.

[q as ill Table 32; efl'ective length, about 23 cm.]

No.

1

2

3

4

5 

6

7

8

9

10

11

12

13

14

15

16

17

19

20

2pX10«

Centim.

1

 80-6

44

^

I 126-5

J

rt

Microhm.

f 8460

8430

8010

7950

8010 

8460

8400

8510

7920

. 8170

r 27860

27710

\ 28000

27490

[ 28400

(- 2807

{

2807

2830

2808

't

°C.

[ 28

1

29

1

1 29

J

",

Microhm.

 790

 820

-860

 850

 830 

 800

 800

 750

 800

. 780

' 2810

 2610

 2620

 2590

 2590

(

 590

 570

 810

 620

aX103

' 1<7

1

I"

ut

S

Microhm.

(- 41-7

41-7

39'3

39-3

39-4 

42-0

41-5

41'9

39-2

. 40-8

40-5

40-3

40-7

40-0

41-3

(

33-3

33-4

33-8

33-5

^

Microhm.

 4-2

 4-3

 4-4

 4-4

 4-3 

 4-1

 4-3

 4-1

 4-3

 4-3

 4-6

 4-2

 4-3

 4-1

 4-1

 7-7

 7-5

 10-5

 8-0

1 Cf. Bulletin U. S. Geol. Snrv. No. 14, p. 94.
BAituaJ SECULAR ANNEALING OF HARD STEEL. 79

SUMMARY.

54. Summarizing the results of Tables 32 and 33, it appears that 

during the 37 months between the two series of observations the specific 

resistance of the rods has fallen from 4G-5 to J42-5 in case of the thin 

rods (diameter <«08 centim.) and from 43-7 to 35-4 in the case case of 

the thicker rods (diameter .13cm.). Hence the variations are a decrement of specific resistance amounting to some 10 or even 20 per cent 

in the extreme cases. This may be stated succinctly as follows: 

Mean atmospheric temperature acting on freshly quenched steel for a 

period of years produces a diminution of hardness about equal to that 

of 100° C. acting for a period of hours. Similar results have been suspected for magnetic measurements; but such results are very much 

less easily interpretable than the electrical data of Table 33; for earlier 

measurements prove conclusively that the electrical variations in question are sufficient evidence for the occurrence of concomitant changes 

of hardness; volume, carburation, etc. Finally, the above results show 

that the method of tempering magnets proposed by Dr. Strouhal and 

myself warrants the steel against secular structural instability for a 

time certainly exceeding three years.
CHAPTEE VII.

THE VISCOSITY OF ELECTROLYZING GLASS. 

APPARATUS.

55. The apparatus by which I endeavored to throw light on this question is represented in Figs. 5 and 6. As regards principles involved they 

are identical with my earlier apparatus. Hot and cold parts of a glass 

tube abc are counter twisted. To accomplish this with least amount oi 

breakage, the ends of the tube are clamped between parallel thin boards, 

A and S, and cemented with mastic. A being fixed, torsion is applied 

at B. The amount of this is never very large and it may be gradually 

increased by a screw adjustment acting against a radial lever in connection with B. The experiment is troublesome, as the brittle glass 

tubes frequently break. To heat any part of abc, it is inclosed in one 

of my boiling tubes, dddd, containing mercury, GG, which may be 

kept in' ebullition by the ring burner RE. The mirror N, adjustably 

fixed between hot and cold parts of abc, registers the amount of viscous 

deformation. The method of passing current through the tubes is different in the two figures. The more complicated arrangement in Fig.

5 secures greater constancy of temperature along cold parts of the 

tube, all hot parts being above. The core of the tube abc is partly filled 

with sodium amalgam, as shown at/f"/', and one terminal of a dynamo, 

or a Grove battery, connects with this at/'. Again the tube abc is surrounded near its middle by a funnel-shaped cup FF, also containing 

sodium amalgam. This can be drawn up into the central tube gg, closed 

above by aid of an exhaust pipe attached at E. The other terminal of 

the dynamo is in connection with F, as shown at h. ° When this current 

is made, it therefore passes in at/, into the core of abc, through abc, into 

the core of gg, into the cup F, and thence back to the dynamo. In Fig.

6 the mechanism is much simpler. The tube abc is fixed in dddd with 

a plug of plaster of paris, p, and abc is immediately surrounded by the 

ebullition mercury G. The current as before passes in at /', through 

the walls of abc into G-, and thence via h to the dynamo. Some care 

must here be taken in screening M, the mirror. In general a number 

of screens are to be disposed in ways which easily suggest themselves. 

80
DARUS. ] VISCOSITY OF ELECTROLYZING GLASS.

RESULTS.

56. In Table 341 have given iny first 

results with the apparatus, Fig. 5. A 

battery of 10 Grove cells was used as 

a source of current. Warburg's1 device 

of sodium amalgam electrodes was not 

known to me at the time, and I here 

used simple mercury for the purpose. 

The current in this case was originally 

about '01 ampere, but fell off rapidly 

to -001 ampere, and finally vanished 

altogether. The results of the table 

were obtained during the period of current; and although in later experiments I applied both dynamo and intermittent currents, the effects were nil. 

Warburg (loc. cit.) has shown that glass 

partially electrolyzed is a condenser of 

very measurable capacity, the dielectric 

being filmy silica. In the table, L is 

the length of the-tube, a the length 

of the hot part (temperature 0=360°), 

and Ic the length of the cold part (temperature 6'=25°), respectively. The 

mirror is at a distance V above the lower 

end. The rate of twist is r. Finally pi 

is the outer radius, p2 the inner radius, 

q the material section of the tube. To 

understand the progress of the experiment it is necessary to consult the time 

column. The viscous datum has the 

same meaning as above, except that in 

the present instance it refers to relatively very large sections q. Hence 

the smaller amounts of viscous motion 

observed. Moreover, in case of glass, 

T can only be chosen vjery small, if liability to rupture is to be avoided.

In Table 35 the dimensions of apparatus are nearly the same as in Table 

34. Twist, however, was considerably 

increased, almost sufficiently to produce 

rupture; and, moreover, sodium amalgam is here employed. The result was 

a current of the uniform intensity of 

0-02 ampere traversing the glass.

A number of other similar experiments were made, all of which led to

1 Warburg: Wiecl. Ann., xxi, p. 622, 1884.

Bull- 94 0

d,
82 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

results of the same indecisiAre character. 

With currents of the small intensity given 

(<0-02 ampere), viscous effects can hardly 

be expected to be discernible Avithin the small 

interval of observation. If large intervals 

were chosen constancy of temperature in 

case of the apparatus given could not be 

guaranteed. The results of Table 34 are 

such as to suggest the actual occurrence of 

a viscous effect of current. This is not substantiated by Table 35. I can not, however, 

regard these results as conclusively negative. It is difficult to avoid contact between 

the tubes ale and gg in Figure 5, without 

choosing for the latter a tube inconveniently 

wide. For this reason I abandoned this apparatus and made the further experimentation with that of Fig. 0. It will not be necessary to give the data in full. They are 

again indecisive, because the viscous motion 

is too slight for sharp discrimination. The 

method of work being such that the rate of 

twist was successively increased until rupture finally ensued, it appears that the experiment Avas carried quite up to the limits 

of attainable accuracy. In Table 30 I indicate the nature of the results for the case of 

an extreme intensity of twist, alter which the 

tube broke.

INFERENCES,

57. To summarize: When the available 

current can not be increased beyond the 

small datum given in the tables, it is improbable that viscous effect of larger value 

than one or more per cent is possible; but, 

to discern such small differences, the viscous 

motion must be very much more rapid. In 

other words, very fliin-tcailed tubes of small 

caliber are to be chosen. In such a case 

the intensity of current as well as the viscous deformation will be effectively increased. The difficulties of experiment 

Avith thin tubes are very great, so that I 

am obliged to abandon further research at 

present.

In conclusion I may insert some remarks 

relative to the conditions under which increased viscous motion during the passage 

of current may be expected. Prof. J. J.
BAKUS.] VISCOSITY OF ELECTROLYZING GLASS. 83

Thomson and Mr. Newell 1 have shown that for small electromotive 

forces the leakage in case of a liquid dielectric obeys Ohm's law, thus 

indicating that the molecular break-up was merely directed, but not 

produced, by electromotive force. On the other hand Quincke, using 

much larger electromotive-forces, finds that the leakage, c;eteris paribus, takes place according to some higher power than the first of electromotive force. Hence in this case the electric field is actually instrumental in dissociating molecules.2 Since Oh m's law is rigorously obeyed 

in electrolytes, it is questionable whether electromotive forces of ordinary value can produce viscous effects even in case of solid electrolytes, 

for the rate of break-up is not thereby increased.

TABLE 34. Viscosity of electrolyzhig glass. Hg terminals.

L=95' =95cm:m ; ; a=]5 a=]5cmcm ; ; fc=45 fc=45lrmlrm ; ; ( ( 2 2 pp, (H 1 r=0'40cm

(/_40cm. 0=:.tUO° ; «' 25° < 2 p^O-3

r=0'003 (

Time.

12h 10'" 

20

23

23 

26

26

29

29

32

32 

35

Current.

1 off 

J

} -f

j ,

5 °H 1

,

5 on (

} * I

*-*'

 xio3

T

o-o

18-0 

29-7

43-0

43-0 

56-3

57-0

67-0

08-3

78-3

77-7 

82-3

Time.

12'' 35'" 

38 

38

41

41 

44

44

47

47

50

Current.

I » I

5 ° 11 \

I '" {

, .

5 ° fl 1

, .

1 ou I

 XIO'1

T

82'3 

 87-3 

87-3

90\7

90-3 

92-3

93'0

94-3

94'3

96' 3

Now, unless the electric field be of sufficient intensity to produce a 

marked change in the motion, i. e., the free path of the ion, it is not 

probable-that such a field will modify the viscosity of glass. Fields of 

small intensity can not increase the molecular instability. Hence tlie 

experiments of the next chapter, the character of which is nearly the 

converse of the present experiments, are better calculated to show positive results.

TABLE 35. Viscosity of electrolysing glass. Na-amalgam terminals.

Time.

3" 20'" 

32

41

45

47

49

49

50

50

51

Current.

] f

[ off \

1

. I

j on J

, ,

1 °ft 1

*-*' 

 XIO1

T

o-o

5-2

6-8

8-4

8-8

8-4

8-4

9-0

9-0

9-2

Time.

3h 51m 

52

52

53

53

54

54

55

Current.

1 »"{

i - i

> on 1

I Off I

0 *' 

 -X101

T

9-2 

9-4

9-4

9-6

9-6

9-G

9-6

9-6

1 Thomson & Newell: Proc. Roy. Soc., xui, p. 410.

2 Of. J. J. Thomson: Application of dynamics to physics aud chemistry, p. 292.
84 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

TABLE 36. Viscosity of electrolyziny glass. Na-amalyam terminals.

9=360°.

fl' 25°. 2Pj =-40

Current, 0.02 ampere.

34m . . .

36.....

36..... 

38.....

DO

40.....

40..... 

42.....

42.....

44.....

44..... 

46.....

 | off..-.

> on ....

| off....

> on ....

| off....

> on ....

*-(/>'

1-0

1-6

1-8

2-4

2-6

3-2

46.....

48.....

48..... 

50.....

50.....

52. ....

52..... 

54.....

1 54.....

56.....

56.....

58.....

| off....

> on ....

j

> off....

> on ....

| off....

> on ....

*-*'.,

T -^ iv

3-8

4-8

5-2

6-0

6-8

7.6
CHAPTER VIII.

THE ELECTRICAL RESISTANCE OF STRESSED GLASS. 

INTRODUCTORY.

58. The thermal relations of the resistance of glass, originally 

studied by Buff, 1 have more recently been made the subject of research 

in memoirs by Beetz,2 Foussereau,3 Perry,4 Thomas Gray,5 and others. 

Warburg's6 experiments, however, throw new light on the inquiry, by 

showing that the apparent polarisation evoked by the passage of cur 

rent is due to a layer of nonconducting silica depositing at the anode. 

If this be continually dissolved by an electrode of sodium amalgam, 

the apparent polarization is so far removed that an almost constant 

current may be kept up indefinitely. If the film be not removed, conduction soon ceases and the glass behaves like a condenser of measurable capacity.

The effect of temperature on the conductivity of glass has thus been 

mapped out with considerable detail, and it will be superfluous to add 

new data in the following chapter. I purpose therefore to confine 

myself narrowly to the effects of stress 7 on electrolysing glass, kept as 

nearly as practicable at different constant temperatures between 100° 

and 360°.

APPARATUS.

59. The apparatus for these measurements are shown in Figs. 7, 8? 

9, 10, 11. Figs. 7 and 8 are simpler and adapted to 300° and 100° 

respectively. Figs. 9 and 10 are intended for experiments with aniline (180°) or other nonconducting fluid, boiling at higher temperatures; and the last apparatus, Figs. 10, 11, are differential in kind.

As before, the ends of the tube abc ( Pig. 7) to be operated upon are bent 

hook-shaped, and then fastened by screws and resinous cement between

'Huff: Lieb. Ann., vol. xc, 1854, p. 257.

"Beetz: Pogg. Ann., J'ubelbaud, 187-1, p. 23.

'Foussereau: Jour, do pliys., IT, vol. xi, 3883, p. 254.

'Perry: Proo. 15 oy. Soc., vol. xxiii, 1875, p. 4(iS.

6T. Gray: Proc. Roy. Soc., vol. xxxiv, 1883, p. 199.

6Warburg: Wied. Aim., vol. xxi, 1884, p. 022; ib., xxxv, 1888, p. 455.

'Reference may here be made to J. and P. Curie (C. 11., vol. 91, pp. 294, 383; vol. 92, p. 350, 1881; vol. 

!)3, p. 1137,1881), and to Hankel (Wiod. Ann., p. 610, 1831), who show that in corUin lieiuiliedral crystals longitudinal compression is accompanied by the manifestation of electromotive force. Curio's 

very recent work is summarized in the Beiblatter, vol. 12, p. 857 to 807, 1888.

85
86 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94

slabs of wood A and B. The upper one is fixed; the lower, JS, provided with a hook from which a scale pan may be hung. In the experiments made, the load P was gradually increased as far as 20 kg. To 

heat the tube abc, and thus promote conduction, I used a ring burner

-B-B, as before. G G-, the ebullition liquid (here 

mercury), is contained in the boiling tube d, 

to the bottom of which the experimental tube 

abc is cemented with plaster of paris. Glass 

is electrically so sensitive to changes of temperature near 300°? that great care must be 

taken to keep the flame of the burner constant, 

and the ring is to be fixed in position relatively to the tube. Any disturbance of this 

symmetry during loading produces a periodic 

thermal error, the effect of which may be excessively large as compared with the stress 

effect to be measured. Finally, the current 

when made passes into the mercury within 

the tube abc at /', then through the walls of 

the tube into the ebullition liquid G, and 

thence, via h, back to the battery. At 360° 

the resistance of this arrangement was less 

than 200 ohms, so. that aside from temperature fluctuations the measurement is easy. 

With a single Daniell and a mirror galvanometer, the current observed is sufficiently constant to admit of direct measurement. From 

this the resistance may be deduced. When 

the liquid boils violently, resistance is variable, probably from the fact that a film 1 of 

mercury vapor of variable thickness envelops 

the metal and interferes with the uniformity of 

contact. The resistance for this case is larger, 

even twice as large, as when the mercury is at 

incipient ebullition. When the apparatus is 

loaded and unloaded alternately, relatively

no. 7.-Apparatus for testing tbo long and regular fluctuations of temperature 

viscosity of stressed glass. . are Of uo disturbing effect, the stress effect 

being superposed On the long undulation.

EXPERIMENTS.

60. Data for 350°. The scale deflections under the stated conditions 

are given below. From the many data I will select those of later date, 

these results being less liable to inaccuracy than the earlier data.

1 1 have thought of using this observation as a boiling-point criterion.
BAHUS. ] RESISTANCE OF STRESSED 

TAHLF, 37. Eesistance of (/lass across Uic lines of sir ess.

2p 2 -40 . .Resistance, 500 ohms.]

Time.

h. in.

2 8

10

12

32

13

15

16

18

20

22

20

27

Load.

kg.

0

0

0

5

5

5

0

0

0

5

5

0

Deflection.

cm.

5-70

5-40

5-20

5-]0

5-10

5-10

4-85

4-55

4-28

4-40

5'40

5-35

Time.

in.

29

31

32

34

36

38.

4.0

42

43

40

47

51

Load.

fcj.

0

0

5

5

5

0

0

0

5

5

7

7

Deflection.

cm.

5-10

4-90

4-60

4-60

4'65

5-10

5-60

5-90

5-80

5-30

5-25

5-00

Plainly the chief fluctuations here observed are due to temperature; 

but whatever the stress effect may be, its amount can not exceed a few 

per cent of the resistance of the glass sample. This appears quite as 

clearly in other results of the same kind, which need not be summarized 

here.

61. Data for 100°. In consequence of the thermal discrepancies 

enumerated, I made the next experiments at 100° in a steam bath. The 

resistance encountered under these circumstances is, of course, very 

large. I measured it at about 20,000,000 ohms in case of the apparatus, Fig. 8. Here the tube to be stretched, afec, is surrounded by a 

wider tube, gg, closed above and below. Both tubes contain sodium 

amalgam, protected from moisture 1 by a layer of paraffin, m. Steam 

enters at the top and is discharged at & so that the apparatus is drained 

of condensed water. In other respects the present apparatus resembles 

the above. The scale pan is attached at P. The results for this case 

are much more uniform. I give the following example:

TABLE 38. Resistance of .stressed glass 

2p2=-40cm . Z:=15cm. Eesistance, 20 megohms, approximately.]

Time.

h. m.

10 50

53

55 

60

11 07

10

Load.

*g.

0

0

0 

0

0

0

Deflection.

cm.

5-50

5-45

5'25 

5-33

5-30

5-28

Mean.

cm.

}

I 5-30

J

Time.

in.

12

14

17 

20

21

23

Load.

kg.

20

20

20 

20

21

21

Deflection.

cm.

5'35

5-35

5-40 

5.33

5-38

5-37

Mean.

cm.

. 5-36

Tube breaks.

1 If gg contiiins the kathode, it may be filled with mercury instead of amalgam.
88 THE MECHANISM OF SOLID VISCOSITY. [BULL. 04.

Iii these results the resistance, after attaining a constant value, decreases by about 1 per cent when the load is added. It can not, however, be affirmed with certainty that this decrement is the true electrical 

effect of the stress increment. All I have done is to narrow down its 

value to the order of 1 per cent.

62. Data for 185°. My next experiment was made with aniline. The

\

S' -'

FIG. 8. Apparatus for testing the viscosity 

of stressed glass.

FIG. 9. Apparatus for testing the viscosity 

of stressed glass.

apparatus is shown in Fig. 9. Similar parts' are lettered as in the 

preceding figures. The aniline is contained in the boiling tube rf, cj. 

The experimental tube abc being tied to the fixed central tube gg of 

the apparatus by a piece of rubber tubing, m, it is easy to surround both 

the inside and outside of cube with mercury. Current passes in at /' and
HAtlUS. ] RESISTANCE OF STRESSED GLASS. 89

out at h. Ebullition is kept up with sufficient intensity to just fill the 

tube d with aniline vapor, which condenses in the exit tube $', and then 

runs back. Two Grove cells were found sufficient for the experiment, 

the observed resistance for this case being about G0,000 ohms.

TABLE 39. Resistance of stressed glass. 

' [2p, = -63 . 2p2 =-40<"°. Z=6«'». 6=180°.]

Time.

h. m.

3 21

23

25

30

31

35

36

40

41

45

Load.

kg.

0

0

4

4

0

0

10

10

0

0

Deflection.

cm.

23-6

23-7

24-1

24-2

24-0

21-4

25-5

24-2

24-3

24-8

Time.

h. m.

3 47

50

51

55

 56

GO

62

63

67

08

Load.

leg.

10

10

15

15

20

20

0

20

20

21

Deflection.

cm.

24-1

24-0

24-0

24-2

24-3

24-1

24-3

24'5

24-3

Breaks.

These results do not certainly indicate any electrical effect of the applied stress at all. They narrow down its possible value to about 1 per 

cent, thus corroborating the results at 100°.

63. Results of twisting. After making these experiments, the general 

character of which is negative, but not conclusively so, I made a variety 

of similar attempts to obtain an electric effect of twisting, but I arrived 

at no definite results,=although I carried the experiments forward to the 

point of rupture. I omit the data.

64. Differential apparatus. Having these results in hand it appeared 

probable that the work could be carried to a greater pitch of nicety by 

comparing strained and unstrained glass simultaneously.

The apparatus with which most of my definite experiments were 

made are shown in Figs. 10 and 11, and are differential in kind. The 

resistances across equal parts of the walls of two nearly identical glass 

tubes, respectively stressed and unstressed, are compared. These tubes 

are shown at abcF and elchf. The ends proper are bent hook-shaped, 

and those of the glass tube to be operated on, fastened by aid of screws 

and cement, between slabs of wood A and 73. A is fixed; B provided 

with a hook, P, from which a scale pan may be hung, or with, a lever 

arrangement for twisting. In the experiments made the load was gradually increased as far as 20 kg., but the tubes were strong enough (theoretically) to sustain about three times this weight. The remainder of 

the figure shows the devices for heating and for passing the currents. 

Fig. 10 is adapted for high boiling points (aniline, etc.), Fig. 11 for 

steam. An apparatus similar to Fig. 10 was used for mercury. In 

Fig. 10, Cr is the ebullition liquid, heated by a G-ibbs's ring burner RR
90 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

surrounding-the wide glass tube dd. A narrower glass tube gg, closed 

below with a perforated cork through which pass the experimental 

tubes dbc and ekli, is partially filled with sodium amnlga-m. This is 

practically one terminal of the battery, the wires connecting at_p. The 

other terminal, after passing through the respective coils of a differeuFiG. 10. Apparatus 

for 200°.

FIG. 11.. Appparatus 

for 100°.

tial galvanometer, connects at m and/with the sodium amalgam contained in the experimental tubes abc and elch.

The notation in Fig. 11 is the same as that in Fig. 10. The two 

forms of apparatus are essentially identical, except that in Fig. 11 it 

is expedient to pass steam through dd, the vapor entering at 8 and
BARCS.] JIESISTANCE OF STRESSED GLASS. 91

leaving the apparatus at 8'. For reasons stated below, § 67, it is desirable that the menisci of the amalgam contained in aboF and elchf, Fig. 

10, be visible above the level of the upper cork of the tube del. The 

amalgam in #</, Fig. 10, should be submerged below the level of Gr. 

Inasmuch as sodium amalgam is necessary only at the anode, ordinary 

mercury may be used at cathodal parts, and these may therefore be 

exposed to hot air or steam without annoyances. To summarize: Current arriving at m and / passes into the sodium amalgam core of the 

tubes abo and efc/t, thence across the walls of the hot parts of these 

tubes into the mercury surrounding them, and finally via p back to 

the battery. Regarding other apparatus, cf. § 69.

65. Results for torsion. I commenced work with torsion experiments 

of which I may indicate something here. A battery of 10 Grove cells 

was used and the analine at Gf, Fig. 10, kept both below and at the 

temperature of ebullition. The deflection of each coil alone being 16-4cm , 

ifc was found that the differential action (nearly zero) could not bo modified by twisting more than 0-02cm . Hence the specific electrical effect 

of twisting can not be greater than about 0-1 per cent. The resistances 

encountered in these cases were about 200,000 ohms. Profiting by this 

preliminary experience, however, I was ultimately able to detect and 

measure the effect of torsion on electrolytic conductivity, using a different and more sensitive method to be indicated below, § 69.

66. Character of traction effects. In case of traction, the data decisively indicated an increase of conductivity proportional to the pull. 

But this result is necessarily complex in kind, and must be carefully 

scrutinized before its true signification can be stated. I will therefore 

give my experiments in chronological order, the first series being made 

at 185° (aniline), the second at 100° (steam), the third series finally at 

360° (mercury).

One remark may be made at the outset": Inasmuch as the electrical, 

effect of traction is persistent with the traction, and is an increment of 

conductivity, it can not be due to temperature. For the extension of 

an elastic solid like glass l produces temporary cooling, § 70.

67. Results for traction. The resistance across the walls of the experimental tube at 190° was about 100,000 ohms. In case of intense ebullition, the temperature is not fully constant. It is therefore desirable 

to use the apparatus, Fig. 10, just below the boiling point of aniline, 

and to bring the plane of the ring-burner slightly below the plane of 

the ebullition liquid G. Parts of the apparatus which are not to be 

heated are screened with asbestos. In this way a nearly stationary distribution of temperature is reached.

Under these circumstances, when a weight of 18 kg. is alternately 

placed on the scale-pan and removed from it by mechanism, thus subjecting the tube to periodic pulls of the force given, a definite and persistent oscillation of the galvanometer needle ensues synchronously

1 Cf. Sir William Thomson's Coilectod Papers, vol r, p. 308.
92 THE MECHANISM OF SOLID VISCOSITY. [CULL. 94.

with the period of stress. The amount of this oscillation was found to 

be equivalent to a resistance-decrement of 1,500 ohms for the stressed 

tube. In other words, the effect of the pull of 18 kg. is a diminution of 

the resistance of the stressed tube amounting to about 1-4 per cent. 

These experiments were repeated many times with practically the same 

results; e. g.:

P = 2 kg., resistance reduced -4 per cent 

P = 15 kg., resistance reduced 1.2 per cent 

P = 20 kg., resistance reduced 1'4 per cent

data in which the oscillation of the needle was made the basis of comparison. They betray a somewhat wide margin of error, because glass 

at 190° is exceedingly sensitive even to trifling changes of temperature. Nevertheless, the data are sufficient for the present purposes, 

and work of a more precise character with high-temperature vaporbaths seemed to me to be superfluous. By using a more sensitive galvanometer such measurements can be repeated at 100° with facility 

and much greater precision.

68. Discussion of these results. The result obtained is clearly a superimposed effect, being due in part to the elastic change of dimensions 

during stretching, and in part to the direct action of stress in promoting molecular break-up. It is therefore necessary to estimate the 

value of the former influence.

The radii of the tube being p1 =-26cm and p2 =*19cm, the section is 

about #='lcm3. Supposing the tenacity of glass to be 6-5 xlO3 dynes 

per square centimeter, this tube should bear 05 kg. Tubes are rarely 

free from imperfections, such as result from insufficient annealing, and 

it is moreover difficult to apply traction in an experiment like the present without some flexural or other strain across the section (tendency 

to be crushed between the slabs AS at the supports, for instance). 

Hence, I found it practically difficult to strain these tubes with more 

than a pull of about 25 kg. without producing rupture. But from all 

this it appears clearly that the longitudinal extension produced by 

18 kg. is much below the maximum for the given dimensions and mean 

strength of tube.

If the tenacity of glass be 6-5 xlO8 and Young's modulus 5-5 xlO11 , 

the values given by J. D. Everett, 1 then the maximum longitudinal extension is -0012. Again, since Poisson's ratio for glass is nearly £, it 

follows that the corresponding radial contraction is about -0003.

Finally, the resistance R of a hollow cylinder, of length i, radii p^ and 

p2? and specific resistance s, to conduction across the walls of the tube 

is (M being the modulus of Brigg's logarithms) :

R = log Pl/p2 = <3GG5 10ff P}lp'2 ~ ' -W

To evaluate the resistance effect of elastic change of dimensions, R is

Everett;: Units and Pliys. Constants, p. 56. Tlic.se data are mlucud from Kuuldiio's " Rules and 

Tables," p. S95.
BARUS.I RESISTANCE OF STRESSED GLASS. 93

to be regarded as a function of Z, pi and p2 . In view of the symmetrical 

occurrence of the last two variables, and if the simplifying relation 

4(5p1 /p1 =4^p2/p2 =(5V^ nearly, it follows that dR'IR=(dR'/dl)fil/R+ 

(dR'/dpl )6p] /R-{-(dR/Jdp2)dp2lR= 6l/l, where the accent lias reference to elastic change.

Nevertheless radial contraction enters in case of an apparatus of the 

form Fig. 10, in which decrease of bore during traction lengthens the 

column of mercury contained. If A be the length of this column before 

stretching, its length during stretching is i*(.l+2#pI /p,)=A(l-f (1/2) 

61/1). Hence, in consequence of elongation of the mercury column, 

SR"IR= (h/2l)6l/l, nearly, where I is the length of the hot part of 

the column. Hence, the elastic discrepancy is

In none of my apparatus did A exceed '2-51. Moreover, A is always one 

shank of a U-tube. Therefore -003 may be assumed as a decidedly 

superior limit of the numeric of equation (2).

Hence, in an extremely unfavorable case, the resistance effect due to 

elastic change of dimension ( -30 per cent) is only about one-fifth of the 

observed effect of traction ( 1-4 per cent) produced by a pull much 

below the tenacity of glass, the said pull (18 kg.) being certainly not 

inore than one-half the maximum, load. These effects are very different, and it follows that the decrement actually observed is principally 

due to decreasedmoleoular stability superinduced by stress. In equation (1), 

s is therefore the variable whioh chiefly responds to the action of stress. 1

To obviate the troublesome occurrence of <5R"/R, the column of 

mercury in most of my experiments was made so long as to extend far 

above the zone of conduction of the stretched glass tube (see Fig. 10). 

In the apparatus for steam. (Fig. 11) the menisci of the column are 

advantageously raised quite above the cork. In such a case 6R"/ll 0, 

and the elastic discrepancy is simply dl/l.

In one respect this reasoning is deficient. It does not take into 

account the changes of elastic behavior of glass due to the heating to 

190°. Tabulated constants for this large interval are not available.2 

Hence special cathetometric measurements must be made. At 190° 

this is difficult, and for these and the other reasons given above (§67), it 

is expedient to refer to the complete set of measurements at 100°. (§ 09.)

'Put P] = p + e and pj = p e; ' PI/PJ = 1-1- 2c 'p nearly. 

Then

dR il dR ie _ &l ,.- <5e/e

~dl Ji + de li~~'l~ " /, . P \, " .. (2)

Here p, the mean radius, is supposed to remain constant., and the ofl'ect of traction is therefore an 

increment of length fsl and a decrement of the moan thickness, 2e, of the walls of the tnhe. Now, the 

value of (JR'/de) &e Ji is relatively very small. Hence, &e e = c2e,"2e, .and the radial contraction may 

ho regarded identical. Then the value of Alt', R in equation (2) is

- fR'/R = + ^ "0012 + ^----: = -0014 

Hence t\w. superior limit of the resistance effect duo to elastic change of dimensions, &K'/R .14 

%, hot differing materially from the above.

"Kohlrausuh and F. E. Looiuis (Am- Jour. Sci. nv vol. L, p. 350,, 1,870), give kny-temi.'er.iture. data for, 

metals.
94 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94

69. Traction at 100°. At 100° the results can be made more accurate 

than the above chiefly for two reasons: In the first place, the temperature is easily obtained absolutely constant; in the second, elastic changes 

of dimensions can be directly measured with facility. In Table 40 I 

have given the results obtained with the apparatus (Fig. 11.) The 

method of measuring these large resistances (glass at 100°) is necessarily chosen more delicate than above. I used a high resistance Thomson galvanometer, read off by Hallock's short-range telescope, and 

adjusted for differential work. The needle being practically ballistic 

in kind, the maximum deflections (swing) obtainable by alternately 

adding and removing the loads P were used for comparison (method 

of multiplication.) I then determined the amount of oscillation produced by inserting known resistances into one or the other coil of the 

differential galvanometer. Knowing th'e resistance of each tube (mean 

values) from special and preliminary measurements, I was able to 

deduce the percentage variation of the resistances of glass across the 

lines of stress. Table 40 contains four series of these experiments; i. 

e., two sets of results for each pair of tubes. .K, the observed electrical 

resistance per tube, was found to be about 7,500,000 ohms per tube, of 

which the external and internal diameters were 2pi=-53oat 2/92 ='3Scl", 

respectively. The table gives the oscillations for the divers loads P; 

the corresponding absolute decrement tilt of R, and the relative value 

of this decrement in terms of jR.

The amount of variation here given for glass is somewhat smaller 

than was found at 200° above. In the last case, however, the data are 

less accurate, and definite statements can not be made. In Table 40 

the values for the second apparatus are smaller than for the first, a circumstance obviously depending on the tubes chosen, but Avhich I will 

also leave without further comment.

TABLE 40. Resistance of stretched glass at 100°.

Tubea.

I and II

I and II

in and IV

III and IV

TV

P

kg.

6

10

15

19

G

10

15

19

6

10

15

6

10

15

5

10

Maximum 

oscillation.

cm.

1-05

1-63

2-20

2-90

 87

1-50

2-17

2-91

 29

 74

1-05

 33

 76

1-11

 56

1-33

Sit

Ohms.

 21000

 33000

 44000

 58000

 17000

 23000

 42000

 5GOOO

 6000

 15000

 21000

 7000

 15000

 22UOO

WX&R/K.

 2-8

 4-4

 5-8

 7-7

 2-2

 3'8

 5'4

 7-3

 -9

 2'2

 3-1

 1-0

 2-3

 3-3

 1-2

 2-8

tMethod.

Differential galvanometer.

l>i(lgo.
BARUS.] RESISTANCE OF STRESSED GLASS. 95

This table proves conclusively that, within the given limits of variation,'the resistance decrement experienced by glass is proportional to 

the applied stress. For the given conditions (2pI ='53olll2/92 ='40C111 ) it is 

as high as 380/10° per kilo stress, and is not below 210/10" per kilo 

stress. Since the section "grr-lO01 "2 nearly, it follows that the mean 

relative variation of resistance due to stretching is about 30/109 per 

gram load, per square centimeter of section. Mr. H. Tomlinson,* who 

investigated the effect of stretching metals, finds that for steel, iron, 

and brass the total variations are only about & as large as this, and 

of the opposite sign. Of. §74.

70. Further results at 100°. When the temperature is sufficiently 

constant, for instance, in the case of a steam bath, experiments may be 

made with a single tube. Let a bridge adjustment be so arranged that 

a/'l)=r/R where r is a known rheostatic resistance and R the resistance 

of the tube, the current in the galvanometer being nearly zero. Then 

if 6r/r produce the same maximum oscillation of the needle as SR/R, 

it follows that 6r/r=6R/R. An accurate chart or table of 6r/r considered as a function of the oscillation is therefore first to be constructed 

by aid of the rheostat. This being in hand, the value of $R/R corresponding to any oscillation produced by alternately adding and removing the load on the tube, is given at once. This method may be 

made very accurate, and I was able to obtain not only traction effects, 

but torsion effects, as indicated by the following data. Here r is approximately 53,000 ohms, R approximately 5,900,000 ohms. In case of 

torsion, P denotes the load acting during the alternate twisting and 

untwisting.

TAHLE 41. Resistance of stressed glass at 100°.

Preliminary.

IIP XS > >

 70

rso

3-77

Oscillation.

cm.

 35

 89

1-63

 Traction.

P

kg.

5

10

10

Oscillation.

cm.

 59

1-27

1-86

1WX&R/R

 1-3

 2-8

 4-1

Torsion.

P Oscillation.

leg.

0

5

10

cm.

 22

 79 '

 28

WX6K/K

 5

 0

 0

The traction data dR/R are numerically larger than in Table 40, and 

hence lend greater favor to the views just expressed. The torsion data 

dR/R are of the same sign as the traction data. . In other words torsion decreases the electrolytic resistance. They are of smaller magnitude than traction data and are independent of the load which the tube 

sustains, so far as I could follow them.

*H. Tomlinson: Proc. Roy. Soc., vol. 25,1876, p. 451; ibid., vol. 20,1877, p. 401.
96 THE MECHANISM OF SOLID VISCOSITY. 

TABLE 42. Longitudinal extension of the lubes, Table 40.

Temperature.

°C.

1C0

100°

100°

100"

Load.

*g,

2

0

10

15

2

6

10

15

2

19

2

19

L

cm.

77-53

77-53

77-54

77-55

77-58

77-58

77-00

77-00

77-57

77-59

77-57

77-00

&L/L

10-n X

0

0

130

200

0

0

2GO

200

0

200

0

390

Coefficient of expansion -000008.

71. Dimensional change clue to torsion. To interpret the above data, 

special measurements of extension are necessary. These are given in 

Table 42. They were made cathetometrically and are not intended to 

give more than a safe estimate of the elastic effect in question. The 

glass tube to be examined was surrounded conaxially by a second 

Avide tube of glass, through which steam at 100° continually circulated. 

Measurements were also made at 16°. .L is the length between fiducial 

marks.

Utilizing these values to obtain a superior limit of the elastic discrepancy in Table 40, it appears that tfZ/Z<-0004 and <?/o/p<-0001, these 

data being the largest obtained for the largest load, 18 kg. Hence by 

equation (2), dR'/lK2-5x -0004=-0010. In other words the elastic 

discrepancy is numerically much less than -1 per cent of JR, whereas 

the corresponding mean value for the traction effect in Table 40 (apparatus with tubes I and II, low menisci) is -75 per cent. Again for 

raised menisci (Tables 40 and 41, tubes III and IV), -d/R'/R=dl/l.= 

 0004. In this case the corresponding mean value of the traction effect 

is numerically greater than -50 per cent. In both instances it may be 

safely inferred that error introduced by elastic change of dimensions is 

at most about 1/10 of the decrement of resistance actually observed as 

the effect of stretching.

72. Effect of temperature. I will make a final consideration here, relative to temperature. The thermal effect of traction is negative; its 

influence on E must therefore be a resistance increment, i, e., opposite 

in sign to the effect observed. Nevertheless,, it is desirable to obtain 

some estimate of its value, which will probably be found; too. small for 

direct measurement. Since P=20 kg, and. 6L/L< .0004C1U , the total 

energy elastically potentialized per linear centimeter during stretching 

is P6L/L < 10000 ergs. Hence, even, if all this energy were coiiverted, 

into heat, the increase of tempera.tu.re resulting; in case. o.f. the given
BARCS.] EESISTANCE OF STRESSED GLASS. 97

tubes (section -10cm2, density <3, sp. heat <-2) would be about 104 /240x 

104 ; *. e., less than -005°. This datum is too small to produce serious 

error even in consideration of the phenomenal sensitiveness of hot glass 

to temperature variations. Estimating that the resistance of glass decreases several per cent (5 to 20) per degree between 100° and 200°, 

the thermal discrepancy can not be greater, numerically, than the elastic discrepancy.

73. Traction at 360°. I have now to communicate the data obtained 

at 360°. This case possesses some points of special interest, because 

the differential apparatus is itself a battery, the action of which enters 

in a complex manner. The electrolytes here are the hot glass tubes 

containing amalgam and surrounded by mercury. The actual apparatus 

was a simplified form of Fig. 10. Fig. 12 presents a clearer diagram 

of parts, in which a and b are the hot glass tubes in question, E

Fio. 12. Apparatus for 360°.

the battery, and D the differential galvanometer. The electrical currents due to E are indicated by the inside arrows; but these currents 

are Considerably reenforced by the action of the element sodium amalgam/hot glass/mercury, as shown by the arrows crossing the tubes a 

and ft. The electromotive force of this element is easily found by reversing the action of E. In an actual experiment I measured NaHg 

/hot glass/Hg=14 volts, a datum someAvhat affected by polarization 

and depending for its value on the strength of the amalgam and the 

purity of the mercury.

Besides this large electromotive force there is another of smaller value, 

due to the fact that the tubes a and 6, with appurtenances, represent 

two elements switched against each other. The currents are indicated, 

Bull. 94 7
98 THE MECHANISM OF SOLID VISCOSITY. [CULL. 04.

by the outside arrows in the diagram, and they are necessarily so circumstanced as not to flow through the galvanometer G differentially. Their 

occurrence is therefore a serious and annoying disturbance, such that 

measurements at 360° can not, without unreasonable painstaking, be 

made with the same accuracy as measurements at 100°. I measured 

the electromotive force in question as aboiit -2 volt, but it is necessarily 

variable, even as to sign, containing as it does the polarization inconstancy of both elements.

Since the resistance of glass near 360° is enormously low relative to 

its value at ordinary temperatures (in some practical cases the apparatus showed less than 1,000 ohms), the extraneous electromotive force 

E can be withdrawn altogether. The present measurements of the electrical effect of traction are therefore made with the NaHg/hot glass/ 

Hg element in the apparatus, Fig. 12, notation being as above, 2p!= 

 53CIU , 2p2=40cm. The small resistance at the boiling point is not available; owing to the formation of bubbles at the surface of contact between 

mercury and glass, the resistance is too variable even for approximate 

measurement. Hence I observed at a lower temperature, encountering 

somewhat larger resistances E.

Even under favorable conditions these data are only qualitatively 

Satisfactory. They are important, however, because they indicate that 

at 300° the diminution of resistance due to traction is not larger in 

numeric value than at 100°; and, since this would be the case if the 

decrements dE observed Avere due to elastic change of dimensions, I 

have here in hand additional evidence against this assumption.

TABLE 43. Resistance of stretched glass at 360°.

Apparatus.

I

III

P

^ 

6 

10

.15

19

6

10

15

Maximum 

oscillation.

cm.

 50 

 50

 70

 70

1-00 

1-40

2-00

E

Ohms.

13COO

17000

ili

Ohms.

-30 

30

50

 15

 31

W3XSR It

 2

9

 4

 4

 1 

1

o

The present experiments are attended with much annoyance. As 

the load increases, the tube is apt to break in such a Avay as to spill 

the hot mercury; and with all reasonable care several tubes are usually 

sacrificed before a full series of observations can be obtained.

SUMMARY.

74. The above paragraphs summarized prove that a solid electrolyte 

like glass is a better conductor of electricity (i. e. manifests smaller 

specific resistance) when in a state of. strain (traction torsion) than
BARUS.] EESISTANCE OF STRESSED GLASS. 99

when free from strain. Inasmuch as the necessary concomitant of 

conduction in this case is molecular decomposition1 and recombination, 

stress of the given kind must promote such decomposition. The rate 

at which molecular reconstruction occurs per unit of volume increases 

nearly proportionally to the intensity of stress; and it may in case of 

traction be carried as far as the limit of rupture of glass amounts to an 

increment of 1 per cent. In case of torsion the effect is not much 

larger than about -yV of this, and the increased break-up due to torsion 

is therefore studied with greater difficulty. The influence of temperature in changing the value of the electrolytic effect of stress is not 

marked. So far as observed the same pull per unit section does not 

increase the conductivity of glass more at 350° than at 100°, if indeed 

it increases it as much.

Again the traction effect in case of electrolytic conduction, being a 

decrement of resistance, is of the opposite sign of the traction effect 

in cases of metallic conduction 2 (increment of resistance). The former 

is also of decidedly greater magnitude. If, therefore, conduction in 

metals is essentially the same phenomenon3 as in electrolytes, then 

the soft metallic state must be singularly well adapted to promote 

molecular reconstruction. This fine adaptation of structure is destroyed by strains of dilatation, by heat, by alloying,4 etc. In the data 

given, the electrical traction-coefficient and the electrical temperaturecoefficient (resistance) are similar in sign and in relative magnitude, both 

in metals and in electrolytes. They are positive in metals and small; 

negative in electrolytes and large. This is additional evidence in favor 

of a volume effect discussed at some length elsewhere.

75. Degree of molecular instability of glass. The chief result of the 

present paper is the emphasis thrown on the fact that, independently 

of the passage of current, such a solid as glass must be conceived as 

undergoing spontaneous molecular reconstruction at all temperatures; 

for, if the reconstruction in question were superinduced by the electric 

field, then the current passing would vary at a power higher than the 

first of electromotive force;, whereas it may be taken for granted that 

currents of the intensity of those discussed above pass through glass 

in accordance with Ohm's law.5 Recently J. J. Thomson,6 among many 

results of his development of theLagrangian function, investigated an 

expression for the number of times w, the electric field is discharged 

at any point, in case of conduction through either metals or electrolytes. If A be the specific conductivity, K the specific inductive ca1 It is best to avoid the term dissociation here. The term molecular reconstruction is used in preference.

a Mousson: Neuo Schweizer. Zeitschr., vol. 15, 1855, p. 33; H. Tomlinson: Proc. Hoy. Soc., vol. 25 

1876 ,p. 451; ibid, vol. 26, 1877, p. 401.

3 J. J. Thomson: Applications of Dynamics to Physics and Chemistry, 1888, p. 296.

4 Am. Jour. Sui., vol. 36, 1888, p. 427.

6 Fitzgerald arid Trouton (Rep. Br. Assoc., 1886, p. 312) show that electrolytes obey Ohm's law accurately.

8 J. J. Thomson: op. cit., p. 299.
100 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

pacity of the medium, then n=27t/]J(/E', where ft is a coefficient the 

value of which is less than unity and depends on the relative time of 

destruction and existence of the electric field. Accepting provisional 

values for ft and K, Thomson computes a table of values for the superior limit of n, in cases both of metals and of electrolytes. From this 

table it appears that n for mercury, for instance, is less than 8 x 1015. 

Similar values for the limit of n in case of glass at the above temperatures of observation, 100°, 200°, 360°, may be deduced. In round number the specific resistances of glass at the temperatures stated were 

108,105, and 5 x 10' ohms, respectively. From this it follows nearly 

that for glass at 100°, M=8xl07 ; at 200°, w=8x!09 ; at 360°, w=16xlOn. 

Thus it is fair to conclude that at temperatures quite as low as 100° 

the spontaneous chemical action, i. e. the continuous rearrangement of 

the molecules of glass, is a pronounced occurrence.

The given value of the frequency of discharge of field, n, may be 

further expressed in terms of the number of molecules m, which break 

up per unit of volume, per unit of time, when the number of molecules 

q per unit of surface, whose disintegration just discharges the field, 

and the mean distance #, over which they are urged by the field during 

the interval between break-up and recombination, are known. For 

n=mx/q; or m=n (q/x). Here a? is a very small quantity, not exceeding the centimeter numeric of the mean free path of the molecule of a 

gas; whereas q is a very large quantity. Hence m is larger than the 

given value of n, even if the above superior limits be 100 times the 

true value of n.

These approximate statistics are the nearest exact statement for the 

phenomenon of molecular break-up which I can adduce, but they suffice for the present purposes. They show that even when glass is 

practically an insulator the number of active molecules m considered 

absolutely is very large and that m need by no means be negligibly 

small even in comparison with the total number of molecules per unit 

of volume.

The above paragraphs prove that the rate at which molecular breakup takes place is appreciably greater wheti glass is under stress than 

when it is not. It is improbable that the system will instantaneously 

state of molecular equilibrium to another Hencej pass from one 

since even in case of very high resistance, such as that of glass at 100°, 

the number of unstable molecules per unit of volume must still be conceived to be very large, it follows that the species of molecular breakup in question may be looked upon as a fruitful cause of viscous deforjuatiou.
CHAPTER 15.

THE ENERGY POTENTIALIZED IN PERMANENT CHANGES OF MOLECULAR CONFIGURATION.

76. Introductory. In the following work a soft annealed wire is 

stretched by a known weight falling from an initial position (strain 

minimum) to the lowest position compatible with the given adjustment 

(strain maximum). If the wire remains sufficiently soft throughout the 

experiment the recoil is nearly zero. Hence the energy expended in 

stretching is to this extent easily measurable; and, if also the heat 

evolved during stretching be measured, the difference between the 

work done on each centimeter of wire and the heat produced per centimeter of wire is the energy poteutialized; i. e., the energy which permanently manifests itself as tensile strain. Using the nomenclature of 

Maxwell's theory of viscosity, the numerical datum thus obtained is 

an expression for the amount of change in the history of the typical 

molecular configuration, the dates being taken immediately before and 

immediately after the tensile stress is applied.

IsTow it is clear that the strain effect of a given^ amount of work done 

must depend on the dimensions of the material. Strain'must be supposed variable with the extension produced in case.of a given sectional 

area, as well as with the section of the stretched wire in case of a given 

extension. At the outset it is difficult even to conjecture in what 

respect these strains, though of a given class, may differ in essential 

details. There is, however, a more interesting phase of these experiments: the strain-effect of a given amount of work done on centimeters 

of Avire will vary, cceteris paribus, with the material acted upon. From 

this point of view the prosecution of the present research promises to 

lead to results bearing directly on the nature (form and mutual relations) of the molecules sustaining strain.

77. Apparatus. In Fig. 13 (7(7, C1 C', the weights (P=30 kg to 60 

kg) by which stretching is to be done are supported on a suitable trap 

door, BB; and the fall of JB.B, when released, is guided by the upright 

slides ss,s's', fixed in the firm base, (7, of the apparatus. I took pains 

to adjust the soft wire ab to be acted on as nearly straight and free 

from initial tensile strain as possible. It was firmly fastened above to 

a heavy cross-timber of wood, J)D, the lintel of a framework which in 

form and purpose closely resembled a gallows. The screw clamp at a 

in the vertically adjustable brass torsion-circle JL, the axle of which 

passes snugly through DD, secures the upper end of the wire. The

101
102 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

lower end is lapped around the hook of the weight pan, bnn, then 

wound around the wire and soldered, care being taken to avoid such 

loops and kinks as might change form during stretching.

A thermo-couple, a/3a*, originally of platinum /pi atinum-iridium, with 

its junction /5 tied on with silk thread on the upper half of the wire ab,

FlG. 13. Apparatus for measuring the thermal effect of stretching.

enabled me to measure the change of temperature due to stretching. 

In later experiments more reliable devices were adopted; cf. § 80. 

Changes of length were measured with Grunow's cathetometer, two 

fiducial marks having been painted on the wire db about 70cm apart. 

At a given signal the catch-board .EF of the trap door BE was jerked
BATiCS. ENERGY POTENTIALIZED IN STRAINS. 103

away, by aid of a rope tied at F and manipulated by an assistant.1 

Simultaneously with, the stretching-1 read oft' tlie temperature-increment in terms of the excursion of the needle of a sensitive mirror galvanometer, and as soon, as this was taken I made the final length 

measurement with the cathetometer. From these both 8'L and 81, i. e., 

the length-increment of the whole wire and of the part betAveen the 

fiducial marks, respectively, were derived.

8L varied between 8cm and 20om, dl between 6CIU and llcm, L being 

about 120cni .

78. Results. In Table 44 I have systematized the results of the 

measurements. Here /> and ^i, denote the radii of the wire before and 

after straining and are computed from gravimetric measurements. P 

is the stretching force; dl'l, the longitudinal extension produced and 

measured between fiducial marks on the wire with the cathetometer. 

fj=PdL/L=P8l/l is the work done on centimeter of length; £, the observed increment of the temperature of the wire resulting. Finally, 

r=J57t/J7 indicates the part of the applied work which is converted into 

heat, the remainder (E E^/E being potentialized. The table contains both P8L/L and Pdl/l, the latter being usually greater in consequence of errors of experiment which need not here be considered.

The heat corresponding to t° being Amct, where A is the mechanical 

equivalent of the water-gram-degree in ergs, m the mass of the wire 

per centimeter, and c its specific heat. I was obliged to take e from 

tables and also for want of data to disregard the variations of c during 

straining.

TABLE 44. Energy potentialized in tensile strains. First method.

Metal.

Brnas .....

Iron ......

Copper ...

2p, 

2ph

cm. 

 1GG2

 1540

 1362

 1310

 1030

 1514

P

a60,000

50,000

40,000

till

(cm) 129

 103

 151

 1G8

 153

 ICO

 154

 087

 091

 084

 087

 0875

 147

 148

 153

 149

PSL/L

Megalergs. 7-5

9-3

9-0

9-9

9-1

8-9

8-95

4-26

4-33

4-17

4'2G

d-91!

5-58

5-51

5-90

5-00

PH,l

Meyalergs. 7-7

9-8

9-1

10-1

9-2

9-0

9-24

4-35

4-50

4-22

4-30

5-88

5-92

6-12

5'98

t

°0 

4-3

4-1

3'9

4-3

 c-o

7-0

4-9

3-8

4-0

4-3

3-5

Q'Q

o-o

5-1

5-5

5-3

5.5

r Et/E

0-40

 30

 31

 31

 45

 62

 38

0-47

 47

 54

 43

 48

0-77

 65

 65

 69

'Mr. Ernest L. Howard bad tli'e goodness to give nie much efficient service during the course of tbo 

present experiments.
104 THE MECHANISM OF SOLID VISCOSITY. [nurx. 94.

In Table 45 I have given the densities of the metals, strained and unstrained, z/s, z/h, and z/lls, referring to wires which are soft, strained 

hard, and softened after straining, respectively. Brass shows a slight 

decrease of volume after straining; but this result, like that of iron, is 

doubtless obscured by differences in the composition, hardness, etc., of 

parts of the annealed wire. Annealing the stretched iron wire scarcely 

shows any volume effect. In case of copper the effect of stretching is 

a definite increase of volume of a few tenths per cent. Small as this 

datum, is, it is well to bear in mind that a like expansion of the wire 

produced by heat, calls for an increase of temperature of 30° or 40°. 

Elsewhere I have shown that it is. scarcely safe to draw conclusions of 

this kind unless data are in hand in great numbers.

TABLE 45. Variation of density of stretched wire.

Metal.

Iron ...... 

Iron ......

Ko.

I .....

II ....

I ..... 

II .... 

I .....

II ....

As

8-419

8-411

7-702 

7-676 

8-881

8-879

AA

8-420

8-419

7-683 

7-681 

8-865

Afts

7-686 

7-681

79. Discussion of errors. A few words on the errors involved are 

essential. Comparison of the values ofPdL/L andP-Z/Z shows that 

the work lost upon kinks and flaws, together with that spent upon the 

framework, is not seriously large so far as the present purposes are concerned. This is also true of the energy elastically potentialized, as 

may be found by direct tests. The satisfactory measurement of the 

thermal datum t, however, is much more difficult. Apparently the 

graduation of the thermocouple is simple, for it is merely necessary to 

make preliminary observation of the throw of the needle of a ballistic 

galvanometer produced by given increments of temperature. The use 

of such graduation is, however, only permissible if the temperature of 

the wire remains constant during the period of oscillation of the needle. 

These conditions are never rigorously given; whereas even in case of 

jacketed wires it is a question whether they are sufficiently given. The 

temperature of the wire increases very rapidly to a maximum, and then 

decreases by radiation, etc., reaching the original thermal value in a 

few minutes. Again the cooling effect of the metallic wires of the 

thermocouple can not easily be allowed for, neither can it be considered 

negligible even in case of filamentary wires. Finally the error of heterogeneity is of serious consequence; for the thermoelectric measurement 

is virtually a thermal exploration of the metal lying-very near the pointjunction. Hence since the wire near such a point may be imperfect 

by reason of flaAvs or composition, so that more or less work is done 

here than at other parts of the wire, it follows that the temperature
BAnus.] ENERGY POTENTIALIZED IN STRAINS. 105

thermoelectrioally obtained is not a mean datum for the wire taken as 

a whole.

Unfortunately the combined effect of the errors stated will usually 

be the cause of too small a value of t. Some assurance of the approximate truth of the results in Table 1 may, however, be obtained by observing that the experiments made are to some extent differential in 

kind. For instance, costeris paribus, for an expenditure of only twothirds the work applied to the brass wire, about the same heat is 

evolved in the copper .and the brass. Sections and thermo-couple are 

here the same and similarly adjusted.

80. Successive stretching. The importance of the thermal datum is 

such, however, that special corroborative measurements are essential. 

To obtain these, the above method was modified in such a way that 

the wire was stretched successively in equal amounts. One end of it 

was fixed and the other fastened on the circumference of an iron drum 

of small radius, p = 09cm . By revolving the latter the wire is stretched 

and the friction of the axle sufficient to keep it so. I chose successive 

angles of revolution, TT, by which extensions <5L/L = -054 each were 

easily produced and could usually be repeated 4 or 5 times.

These accumulating strains are numbered in Table 46, in the first 

and second parts of which the data <5t are obtained by a Pt/Pt -Jr° 

thermocouple with wires 0-05CI " in diameter; in the third part by a 

filamentary iron / brass thermocouple (wires O02cm in diam.). Moreover 

in part 1 the junctions are fastened by binding them down upon the 

metal to be stretched by platinum wire. In parts n and in the junctions are bound down with silk, as in Table 44. In part iv the couple 

is of the kind used in constructing Table 47 below. The data of Tables 

44 and 46 when referred to the same value of 6 L/L agree fairly well. 

Some difference in favor of the silk fastening is apparent. Again 6 t 

increases in proportion as the wire is more nearly stretched to the 

point of breaking. This is in part due to the fact that as the wire 

hardens more work must be done to stretch it. When the wire breaks 

(strain V) the resilience is usually sufficient to increase 6t appreciably 

in consequence of the energy elastically potentialized. Finally it is 

easily seen that, although the mean values of <5t in case of the divers 

metals are not very different, this is not true for the amount of work 

done in stretching. P varies widely, being less in copper than in brass 

and less in initial than in final.strains.
106 THE MECHANISM OF SOLID VISCOSITY.

TABLE 46. Successive stretching. 

[SL/L O- 054 per pull.]

[BULL. 94.

I .......

n ......

in .....

IV......

v. .....'.

i .......

n......

in .....

IV......

i .......

11......

m.....

rv .....

]

st

ri

1-3

2-0

2-2

2-2

0-7

1-7

2-0

1-8

St

0-8

1-0

1-2 

1-2

1-2

2-3

9'fi

2-9

9-a

I

it

0-6

1-4

1-3 

1-6

I.

St

1-6

2-0

1-9 

2-4

2-6

in

St

i ^

1-0

1-7 

2-1

q.n

[.

st

1-0

o.o

2-2 

2-1

g.o

IV.

it

9*0

O.K

3-5

Q.Q

9-ft

2-5

4-0

81. Results of improved methods. The errors discussed in § 79 induced 

me to repeat the work with a thorough change of method, so far as 

the thermal measurements are concerned. To obtain the data of Table 

47, the thick wire «&, Fig. 13, was itself used as one of the elements 

of the thermocouple. The other element Avas a filamentary wire, tv/fc, 

passing from a fixed point, ^, in connection with the terminal of the galvanometer, once around the wire to be stretched (junction, /?), and 

thence to an insulated spiral spring .R, to keep it tense. At the pointy 

/?, where the thin wire lapped around the thick wire, both were carefully brightened and good electrical contact was further insured by 

stiffening the spring H as much as the thin wire permitted. The upper 

end a of the wire to be stretched placed in connection with the other 

terminal tf of the ballistic galvanometer completed the circuit. In this 

way the heat generated by stretching acts at once at the thermoelectric junction of the thick and the filamentary wire, while the latter 

may be chosen so thin as to produce only negligible cooling. Indeed, 

in virtue of friction the discrepancy is apt to be in the opposite direction.

In this arrangement, 1 a special error is introduced by the change of 

thermoelectric constants due to stretching, but this error, for the present purposes at least, is negligible in comparison with the thermoelectric powers copper/iron or brass/iron, being not greater than a few 

per cent.

The notation of Table 47 is the same as that in Table 44. Ep, the mean 

energy stored in the wire per centimeter of length, has been added.

l After making these experiments, I found that a similar method of thermoelectric measurement 

has recently been employed by Wassmuth (Wiener Sitzber., vol. 92 (2), 1888, p. 52). Wassmuth's purposes are distinct from mine.
ENERGY POTENTIALIZED IN STRAINS. 107 

TABLTC 47. Energy potentialised in tensile strains. Second method.

Metal.

Brass .....

Copper . . .

2ps 

2pft

cm.

 1GG

 155

 163

 151

 130

 131

 130

P

 flee, ooo

40,000

50,000

40,000

Sill

(cm.)

 199

 19.1

 182

 153

 153

 153

 143

 143

 084

 086

 089

 032

 031

E

Meyalergs.

11-8

11-5

10-9

C-12

6-12

0-12

5-72

5-72

4-21

4-28

4-47

1-26

1-23

t

°0.

9-1

9-0

8-8

6-8

6-1

6-8

6-0

6-3

4-0

3-9

4-3

0-8

0-5

EtIE

0-55

 50

 58

0-81

 72

 81

 76

 80

0-51

 49

 51

0-30

 22

EP

Megalergs.

5-0

1-3

2-2

0-9

A comparison of the results of Table 44 and Table 47 shows that the 

latter substantiates and emphasizes the results of the former. In Table 

47, moreover, the measurements of the effects produced by stretching 

the same metal are in very much better accord. It is not improbable 

tliat the variations of E^E for the same metal in Table 2 may be due 

to actual differences of hardness or composition, of the annealed wires.

In case of iron two values of P occur and the metal exhibits striking 

differences of behavior in the two experiments. It appears that more 

energy is potentializecl during initial than during final stages of strain. 

For P=40 kg, the' small value of t is only measurable as a superior 

limit. Moreover the extension is here so small that the error due to 

resilience may be 5 per cent.

82. Summary. To summarize: It appears that as much as one-half of 

the work done in stretching up to the limit of rupture may be stored up 

permanently; that the amount of work thermally dissipated varies 

considerably with the metal acted upon, being very large for instance 

in the case of copper (75 per cent), smaller in case of brass (60 per 

cent) and of iron (50 per cent); that in case of the same given metal 

the work done is very largely potentialized during the incipient stages 

of strain and very largely dissipated during the final stages-of strain. 

When stress of a given kind is applied to different metals, the total 

amount of energy which can be stored per unit of section, per unit of 

length up to the limits of rupture, may therefore be looked upon as a 

molecular constant of the metal. Table 44 shows that in case of a 

wire .about J.Gcm thick stretched nearly to the limits of rupture, at 

least 5 megalergs per centimeter will have been stored in case of brass 

and about 1 megalergs per centimeter in case of copper. In iron'14cm 

thick at least 2 megalergs per centimeter are potentialized under the 

same conditions.
108 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

Perusing the present chapter as a whole it will be seen that the 

experiments made are closely analogous to the usual mode of therinochemical measurement. The difference between the initial and the final 

energy of a system of two interacting liquids is the heat evolved during mixing. In solid metals this experiment can be made with a single substance. The reactions are such that energy is absorbed during 

straining; in other words the difference between the final and the 

initial energy of the system of weight and wire is the hea't evolved in 

stretching. It does not follow, however, that the increased intrinsic 

energy of the strained metal occurs in consequence of the formation 

of new molecules of greater intrinsic energy; for the added energy 

may be stored in modified systems of the original molecules, Nevertheless it is interesting to note that the diminished viscosity which 

usually results from permanent strain corresponds to an increment of 

the intrinsic energy. Viscous motion is therefore the result of the 

tendency of the increment of energy to dissipate, since the systems 

within which it is stored are unstable.
CHAPTEE X.

THE CHEMICAL EQUILIBRIUM OF SOLIDS, IN ITS RELATION TO 

PRESSURE AND TO TEMPERATURE.

EARLIER RESEARCHES.

83. In a recent number of the American Journal1 1 communicated 

certain data on the effect of dilatational strain on the electric resistance of glass. These experiments, though decisive as to results, were 

somewhat complex in character; and from their important bearing on 

the chemical equilibrium of solids, I resolved to attack the subject from 

a new point of view. The present work is direct, and I hoped that 

results could thus be reached without necessitating auxiliary hypotheses 

or experiments. In this expectation I deceived myself: the insulating 

oil Avhich transmits pressure to glass shows a pressure-coefficient 

usually much larger than the glass itself. Both must therefore be 

studied. Nevertheless the confirmation of my earlier results which 

the present paper gives is gratifying. I am thus able to carry the deductions one step further. Again, the behavior of liquid hydrocarbon 

insulators under pressure presents many points of special interest in 

relation to the formation and occurrence of ions.

As a result of the investigation of different oils, I have been able to 

increase the efficiency of my screw-compressor 2 in marked degree. By 

using a sticky mineral machine oil, thick enough to be almost opaquely 

fluorescent 3, not only does the screw of my apparatus run more easily, 

but leaks at high pressure are practically absent. Moreover, the gasket of marine glue is not in any measure dissolved (this is the case 

Avith sperm oil), and it therefore lasts indefinitely. Finally, the insulation of barrel and piezometer is now at least as high as 10,000 megohms and need not be less than 1,000 megohms. This is an important 

requisite in experiments like the present.

The special work on the effect of pressure on the electromotive force 

of the cell NaHg/glass/Hg has intrinsic interest apart from its subsidiary purpose as embodied in the present text. From experiments 

to be published in a bulletin of the U. S. Geological Survey, I infer 

that the secret of the relation of the Peltier contact to the Volta contact will probably manifest itself, if a suitable cell, suitably compressed, be carried through a large range of temperature quite into 

red heat.

1 Am. Jour. Sci., vol. 37,1889, pp. 339-351.-

2 Phil. Mag., 5th SOT., vol. 30,1890, p. 338, 

* Possibly uoutiviuiug ruljber.

109
110 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

I gain another inference by comparing the present results with the 

data of my last paper 1 on the effect of pressure on the thermal relations of metallic and electrolytic conductivity.

Finally, the present work is tributary to an extended series of experiments on the relation of melting point and pressure, as will appear in 

vi § 88. Thus it forms an essential part of the work 

i suggested by Mr. Clarence King.

i APPARATUS.

84. Compressor. Hydrostatic pressures as high as 

 ; 1,500 atmospheres were applied. Having found that

 | within the limits of the present paper nothing esseno tially novel was gained by excessively high values of 

| pressure, I facilitated my work by avoiding them 

| as much as possible. 

£ 85. Vapor baths. To obtain different constant

-s temperatures, the tubes were exposed successively 

1 to vapors issuing from water (100°), turpentine 

£ (160°), naphthalene (215°)., and diphenylamine 

| (310°). A serviceable continuous vapor bath for this 

| purpose is also described in the paper last cited. I 

§ need only add that the ends of the brazed copper 

« bath are provided with screw stuffing-boxes of the 

| ordinary kind, in which either asbestus packing or 

| a hollow cylinder of cork may be forced home by

! | the gland. Vapor baths must be removed hot.

 % They then slide off the smooth steel piezometer 

I easily, and without jarring the tube.

^ § 86. Insulation. In the compressor the arrange-

! I merit adopted is that of insulating the piezometer

 g tube from the barrel and compression appurte-

*! nances. Inasmuch as in some of the experiments 

3 the resistances to be measured amount to several hun- 

& dred megohms, the piezometer insulation must be 

perfect to at least several thousand megohms. How 

this was gradually accomplished will be explained in 

§§ 94 et seq. Gutta-percha covered wire and raised 

hard-rubber commutators are essential. Care must 

be taken to insulate the water-jackets which cool the 

ends of the piezometer, and to allow the efflux water to drop into a 

cistern discontinuously. The burners which heat the vapor bath must 

be insulated to prevent conduction through the flame, etc. At high 

temperatures, where the resistance of the glass* will have decreased 

several hundred to one, many of these precautions are superfluous. 

They are always necessary when oils are examined.

1 Am. Jour. Soi., vol. 40, 1890, pp. 210-222.
BAKUS. ] RESISTANCE TUBES. Ill

87. The resistance tube. The original apparatus for measuring tlie 

resistance of compressed glass is shown in Figures 14 and 15, of which

the latter is a diagram. Fi

14 consists essentially of

two coaxial glass tubes, the 

larger completely surrounding the smaller. The diameter of the larger (thickwalled) tube is -4 to -5cm ; 

that of the inner (thincalled) tube is -2cm . They 

are joined along the ring 

a a. Two separate compartments are thus formed, the 

inner of which is filled with 

pure mercury and the outer 

with sodium amalgam, to a 

sufficient length to completely envelop the inner 

tube. The end of the large 

tube contains hydrocarbon 

oil, to protect the amalgam 

against moisture or air 

when the tube is not in 

place, and also to prevent 

the saponification of sperm 

oil and to eliminate condensible air when the tube is in 

place. Mercury and the 

fluid amalgam are to be introduced by aid of the airpump, care being taken to 

boil out all traces of air. 

The mercury of the inner 

compartment is in galvanic 

connection, with the platinum wire bj which in its turn 

connects with the piezoin eter 

tube. Hence b need not be 

insulated. The amalgam is 

pierced by the terminal c, 

completely insulated, from 

the piezometer by the unbroken length of cold-glass tube surrounding the wire. To prevent the 

wire from being pulled out of place during' the adjustments, c is 

sealed in the inside of the insulator tube as shown in the figure. This
112 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

terminal is in galvanic connection with the barrel. It is seen that the 

tube is virtually a galvanic cell, NaHg/glass/Hg, aud is reversible.

Under the influence of hydrostatic pressure the figure of the glass tube is symmetrically reduced in size. 

Hence, with regard to the conduction taking place 

across the walls of the inner tube, the resistance would 

be increased, in consequence of changes of dimensions, 

only by the amount in which the length of the inner 

tube is diminished. In other words, if r=sl/27t~RL, 

where s, ?, E, L denote respectively specific resistance, 

thickness, radius, and length of thin tube, then the 

dimensional effect of pressure is 6r=(s'l/27rE,L) x <5L/L, 

nearly. But all such values (JL/L being less than .1 

per cent per 1000 atm.) are negligible in comparison 

with the relatively large pressure coefficients actually 

obtained (cf. Tables 48 to 55,) and to be interpreted with 

reference to s' s. 

« Fig. 15 (diagram) shows the resistance tube in place.

-2 PP is the tubular steel piezometer, surrounded by the 

| vapor-bath V V, and the cold-water jackets D D and

 | D' D', and filled with the oil O O, by which the pressure 

<E is transmitted. The inner compartment of the glass 

j a tube is at a (mercury), the outer compartment at m m 

^ (sodium amalgam), with petroleum at n n. The termif nal wires are shown at b (cathode connecting with the 

J* piezometer) and at c (anode, insulated). 

I 88. In the course of my work, however, I found it es1 sentialto connect c with the piezometer and to insulate 

& 6; for by thus reversing the tube there is no tendency 

of short-circuiting through, oil and the outer tube. Indeed, so important is this adjustment, that I further 

modified the tube, Fig. 13, in the way indicated in Fig. 16. 

Here the inner compartment is filled with mercury 

to only about 7 cni of the end. The remainder of the 

tube, containing hydrocarbon oil, runs completely 

through the piezometer into the barrel, with which the 

insulated platinum terminal connects. To keep the 

mercury in place, the inner tube is drawn down to a 

smaller diameter (see i, Fig. 3), into which the mercury 

meniscus projects. Air is excluded by boiling the mercury with the platinum wire in place. The latter amalgamates externally, but careful handling is none the less 

advisable. The outer tube, with its filling of sodium 

amalgam, not only envelops the inner mercury thread, 

but extends in both directions as far as the cold parts of the surrounding piezometer tube, Since c connects with this, no current
INSULATION OF OILS. 113

pass through the film of hot oil and the outer glass tube. All currents 

between piezometer and barrel must therefore pass through the walls of 

the inner glass tube a condition which is further insured by making 

SaHg/glass/Hg the acting electromotive force. I have purposely described these precautions at length; and their importance is obvious 

when it is remembered that the oil medium has a larger pressure coefficient than glass, and that the insulation of oil sometimes breaks down 

in marked degree with rise of temperature (§ 103). The effect of cold 

oil can be found preliminarily, when the whole apparatus is cold.

89. Arrangement for testing insulation. I have finally to show tlie apparatus for testing the resistance and pressure coefficient of the liquid 

insulators at different temperatures. This is given in Pig. 17 (diagram), and consists- essentially of a cylindrical steel rod s s, adjusted 

coaxially Avith the steel piezometer PP, containing the oil to be tested. 

Tubes of glass, g g, hold the rod ssin position. Owing to the fact that 

above 200° glass conducts better than most hydrocarbon oils, this insulating arrangement is not quite satisfactory j but by using thin-walled

 cold,-* ------- -- - --hot-- ----- ---

FiQ. 17. Arrangement for measuring the pressure increments of the electric resistanc

insulators.

glass tubes filled with the oil, the data so obtained are sufficient for the 

purposes of the present text, since the rate of breakdown with temperature is accentuated. It is seen that the measuring current passes 

from the piezometer P P, through the cylindrical layer of oil, into the 

rod s s, and thence to the battery. The diameters of steel core and 

piezometer tube being -13 and -G3 centira. respectively, and the exposed 

part 9 centim. long, the specific resistance of the layer of oil is easily 

computed (§ 103).

90. Digression,. By filling the greater part of the closed end of the 

inner tube (Fig. 13 or Fig. 14) with the substance to be examined, and 

the open end as far as e with mercury, the tube is available for the study 

of melting point and pressure. In such a case the forward motion of 

the inner mercury meniscus due to pressure proportionately decreases 

the resistance of the arrangement by increasing the opposed surfaces 

of mercury and sodium amalgam. Increased delicacy is secured by enlarging the bulb at the end of the inner tube. At the solidifying point 

the sample usually undergoes a phenomenal reduction of volume, corresponding, therefore, to a similarly large reduction of resistance. This 

occurrence I propose to use as the criterion of solidifying- point and of 

l, 94 §
114 . THE MECHANISM OF SOLID VISCOSITY. [BULL.94.

melting point. The apparatus is available above 100° under any pressure up to several thousand atmospheres.

The criterion specified is also available when a fine platinum wire is 

stretched through contiguous coaxial columns of the substance and of 

mercury in a vertical piezometer.

91. Resistance measurement. ^Resistances were first measured by a 

bridge method; but owing to the fact that electromotive forces are involved which may themselves vary with pressure, I lost faith in the 

safety of these methods and replaced them by simple circuit methods. 

The errors to be guarded against are primarily in the experiment itself. 

Again, the resistance tube (Figs. 14-16) is well adapted for simple circuit work, since the electromotive force NaHg/glass/Hg may exceed a 

volt, and the only pronounced resistance is in the cell. Only at 100° 

need auxiliary cells be inserted.

Throughout the work the low-pressure or fiducial resistance is measured before and after the high-pressure resistance. This safeguard is 

necessary. From three to five minutes were allowed for the elimination 

of thermal discrepancies. The fiducial resistance is to be measured 

under a pressure of 100 to 200 atmospheres, both to condense the air 

retained in the pump and to make the oil less compressible (§ 116). Not 

much care was taken in measuring the absolute resistances, since the 

inferences of this paper are to be drawn from the increments.

92. Galvanometer. In the high-resistance experiments I used the 

Elliott square pattern of Thomson's high-resistance astatic galvanometer. The readings, however, were made by Poggendorff's method of 

telescope and scale. To adapt Thomson's concave-mirror adjustment 

to this purpose, I compensated the curvature by an ordinary "No. 36" 

concave spectacle glass fixed in front of the mirror, diffuse light being 

suitably screened off. Glass "No. 36" slightly under compensates the 

mirror, leaving some magnification which is not undesirable. How 

far a weak telescope may be made to do the service of a more powerful 

instrument, by virtue of the concave mirror and a lens even weaker than 

No. 36, remains to be seen. With the above adjustment of lens and 

mirror, using a telescope magnifying somewhat'over 20 diameters, and 

a scale somewhat further than 2 meters from the mirror, I obtained an 

image about 4-5 centim. long and sufficiently distinct for all practical 

purposes. Thus, if one volt act in one million megohms, the current 

produced would only just escape detection.

At 200° the galvanometer was suitably shunted.

93. Other adjustments. Eegarding other manipulations, the paper 

cited in § 84 will have to be consulted. Electromotive forces were measured by a zero method.

OBSERVATIONS.

94. Tables explained. Table 48 contains data for the apparent change 

of the resistance of glass with pressure, when the liquid which transmits pressure is ordinary sa,poiiifiable*sperin* oil. Here 6 denotes the
BAUUS,] ELECTEICAL RESISTANCE OF GLASS UNDER PRESSUEE. 115

temperature of the vapor bath, approximately, and R the resistance of 

the uncompressed glass shell. dR/R is the increment of resistance, E 

corresponding to the pressure increment dp, where the initial pressure 

is at least 50 atmospheres (§01). 7c,=tfR/E.djp is the pressure coefficient. To save space, I have taken the mean of the two or three complete triplet observations for each dp given. The table contains six 

independent series of experiments, made at different times and often 

with different tubes. The adjustment, however, Avas in. the main that 

of Fig. 15 reversed.

TABLE 48. Apparent effect of pressure (in atmospheres) on the resistance of glass, in an 

insulating medium of animal sperm oil.

Series No. 

e 

K 

Mean Avx 106

I.

215°.

117X10'<o

182.

I.

215°.

117X103u>

182.

I.

310°.

GXlO'w

137.

I. 

310°. 

CX103co

134.

n.

215°.

122X103<o 

178.

II.

310°.

9X103<o

121.

in.

'2150.

130X103<o

161.

103 X 

SK/R

82

160

213

75

157

217

59 

117

170

61 

A16 

158

67

135

195

49

97

145

85

165

219

<p

470

83"5

1180

455

825

1160

497 

830

1175

470 

845. 

1155

300

750

1070

450

790

'1120

516

1000

1405

106 Xfcr

174

191!

181

167

191

188

119 

142

145

130 

136 

137

171

180

182

112

122

127

103 !

163 !

156

Series No. 

e 

K 

Mean fo-XlO"

m.

31t)°.

116.

IV.

100°.

_

360.

IV.

160°.

_

200.

VI.

100°.

660.

VI.

160°.

203.

VI.

215°.

184.

VI.

310°.

10»(o

140.

103 X 

fili/B

51

99

165

164

330

U2 

102

111

420 

420

127

136

14.1

126

123

127

97

89

Sp

480

877

1320

450

930

5J5

525

610

605 

650

655

644

674

657

691

688

689

639

IWXkr

110

113

125

365

355

217 

196

185

685 

640

194

211

209

192

177

184

143

138

95. Remarks on the .table. A graphic construction shows the charac- 

.ter of these divers series to be identical, though the individual pressure 

coefficients show marked variation. The data of the third series are 

made in connection with the following data of Table 49, in which electromotive forces are measured before and after the resistance measurements, As a rule, the galvanometer needle (Joes not reach its position
116 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

of equilibrium at once; the slow changes registered are probably due 

to gradually vanishing thermal discrepancies (§121).

96. Electromotive force. Table 49 gives results for the effect of pressure on the electromotive force EaHg/glass/Hg. Here 8 is the temperature of the vapor bath, and e the observed electromotive force, in 

volts, corresponding to the pressure 6p, when the initial pressure is 

above 50 atmospheres (§ 94). lc e = de/e * dp is the pressure coefficient.' 

Five minutes were allowed per observation. Special experiments 

showed that e decreases on cooling. The medium for transmitting 

pressure is again ordinary animal sperm oil. Earlier observations were 

discarded, and the results are condensed as far as possible.

TABLE 49. Apparent effect of pressure on the electromotive force of NaHy/glass /Hg.

e

Mean fee xlO6

100°.

230.

*215°. 

7-3.

ip

( 0

I 720

5 °

U080

c ^

I 533

0

t 524

f 0 

] 551

^1010

1

1 1011

f °

I 542

1l033

1 1441

f o

1 540

|1027

U436

eXIO4

5180

5950

4300

5440

10872 

30904

10912

10950

10922 

10968

10996

10924

10976

11008

10924

10972

11004

11024

10912

10968

1 11004

11028

10.X*.

 210

 

245

5-5

_

6-7

7-7

6-8

_

8-0 o J

7-7

8-2

7-2

6'5

9-0

8-3

7-4

e

Mean ke X10G

1 215°.

10-9

310°. 

5-1.

Sp

Q

I 488

5 °

( 992

<1378

c o

I 550

I 505

S °

I 480

ex 10'

11182

11244

11210

11332

11224 

11374

31214

11286

10058 

10672

10666

10706

K».

11-3

11-0

9-7

 

11-7

2-5

. 

7'8

* Before the resistance measurements. 

1 After the resistance measurements.

97. Remarks on the table. To facilitate measurement, the greater 

number of experiments are made at 215°. Polarization was observed; 

and for this reason the measurement of temperature coefficients by 

removing and readjusting vapor baths was not tried. The increment 

of electromotive force is largest immediately after compression (temporary effect), and then decreases to the apparently constant values of 

the table. The converse holds for the decrement on removing pressure. 

At 100° no satisfactory results could be obtained (§ 118). At 310°, 

although the temporary effects were distinct, the permanent effects 

a.re not warranted.
BAKUS. ] PRESSURE COEFFICIENT OF OILS. 117

98. Pressure coefficient of 

sperm oil. Table 50 contains 

results, given on a plan 

identical with that of Table 

48, for the case in which, the..--, 

glass tube (Fig. 14) was removed and the steel rod 

(Fig. 17) inserted. In this 

way the pressure coefficient 

of ordinary sperm oil was 

found. Table 50 also contains results for glass made IOQO 

after the work with oil.

These results are shown 

in Fig. 18, where little circles 

disti n guish the observations 

for oil.

The pressure coefficient of 

sperm oil is therefore decidedly larger, and the specific resistance of this oil is 

usually smaller, than that of 

glass (cf. § 103, Tables 56 

and 57); but the breakdown

of resistance with rise of tern- 6QO 

perature is more marked in 

the latter, case. Nevertheless the data of Table 50 cast 

grave doubt on the trustworthiness of the data of 

Table 48; and hence a search 

must be made for more 

highly insulating liquids. 

For obvious reasons I selected the hydrocarbon oils 300 

of the paraffin series.

99. Pressure coefficient of 

gasoline. Table 51 contains 

data for the insulation and 

pressure coefficient of very 

volatile gasoline.

These results are shown 

in Fig. 19.

The resistance of gasoline 

is therefore enormous as compared with sperm oil, and 

above 100° more than 100 

times that of glass. MoreFIG. 18. Pressure coefficient and temperature for sperm oil 

and for glass.
118 THE MECHANISM OP SOLID VISCOSITY. [BOLL. 94.

over the breakdown of the gasoline insulation with temperature is remarkably slow; but owing to the difficulty of keeping the apparatus 

free from leaks in the case of this very thin oil, I did not make experiments with the glass tube.

TABLE 50. The insulation and pressure coefficient of sperm oil. 

Oo = 10° atm. Pressure coefficient of glass.]

Series No. 6 ' 

R 

Mean 1Q6X foil. 

20°. 

ISXIO6*,

X5700.

1.

100°.

2X10«w

+880

1.

215°.

SOOXlO'w

+330.

103 X 

«R,R

3300 

3500 

8100

6500

2200

500 

550

990

,460

180 

200

230

ip

540 

573 

1240

1140

553

550 

610

1150

550

550 

 600

675

106 xfo.

 6200 

 6100 

6500

5700

4000

910 

890

860

840

330 

330

340

Series ISro.

e

R

Mean 106 X£v

103 x 

(JR/R

ip '

10°Xifcr

Glass tube inserted.

VII.

100°.

240 x l&ta 

620.

.VII.

215°.

500X10sw 

171.

 347

373

90

94

186

570

580

570

560

1000

600

640

157

170

186

A feature of these results is the negative pressure coefficients found, 

which themselves decrease algebraically nearly proportionally to the 

temperature of the oil. At a given temperature the resistance is not 

constant, but decreases; and since the gasoline is discolored when removed from the press, the decrease of resistance is undoubtedly a solution phenomenon. Indeed, I suspect that negative coefficients are 

possibly to be associated with solution (§ 123).

looo

tooo

300

FlG. 19. Pressure coefficient and temperature for gasoline.

100. Pressure coefficient of petroleum. In Table 52 data are given for 

ordinary illuminating oil (petroleum). The glass tube still has the 

form of Fig. 14, reversed. Two sets of experiments were made.
BARUS. ] PRESSURE COEFFICIENT OF OILS. 119

TABLE 51. Behavior of gasoline under pressure. 

[Initial pressure, ^0 =200 atni. Resistance at 20°, 2X10!> w.]

Scries No. 

8 

R 

Mean fcrXlO6

2. ,

100°.

1

450 X 106<o

to

130X10«u

±0.

2.

215°

{

220 X 106w

to

150XlO«w

. -890.

10'' X 

<!R/R

0

-330

 290

 200

 140

-190

Sp

250

250

280

280

220

250

10° X fcr

0

-1300

-1050

 710

_ 640

- 7CO

Series No. 

9 

R 

Mean fo-XlO6

2.

310°.

220 X 10B(o

 1800.

103 X 

8R/R

 380

 550

 580

 550

 590

ip

250

300

300

300

300

10" X kr

 1500

 1800

 1900

 1800

 2000

TABLE 52. Insulation of pressure coefficient of petroleum.

[Initial pressure, p0 = 50 atni. Pressure coefficient of glass.]

Series No.

0

R 

Meanfo-XlO6

3.

20°.

370xlO°a>

+ 1500.

3.

100°.

130X 10'w

+ 820.

3.

215°.

40X10°<o

+ 274.

3.

310°.

!

47X106a>

to

34X106a>

 430.

103 X

SR/R

700 

700

520

134

167

177

 285

 281

 229

 223

 192

Sp

460 

480

580

760

570

590

580

550

570

570

640

520

1530 

1460

890

750

234

929

306

 521

 492

 404

 349

 369

Series No.

8

R

Mean fo-XlO6

10'X

8R/R Sp 6 ,

Petroleum tested again. #n = 200 atm.

4.

100°.

740XlO"(o 

+ 1800.

4.

215°.

+ 560.

4.

310°. 

32X106u>

 340.

560

750

115

193

200

 115

 175 

 100

 105

 140

 115

 130

 105

370

360

310

305

300

300

550

290

523

298

495

280

1500

2100

380

640

. 667

 383

 320 

 360

 300

 270

 383

 265

 380

Glass tube inserted.

vm.

100°.

230X10G(o

+780.

vm.

215°.

200X103w

+ 136.

VHI.

310°.

GOXlO'w

X43.

630

420

84

86

20

34

33

40

570

610

630

600

740

725

6G5

640

880

680

132

142

26

34

50

63

IX.

100°.

109(0

+ 1330.

IX.

215°.

700X103<o

+ 93.

IX.

310°.

140Xl03<o

 76.

400

20

25

36

30

 25

 32

 17

300

300

280

300

300

300

300

300

1330

'

66

88

120

100

 83

 107

 55

These results are sliown in Tiff. 20.
120 THE MECHANISM OF SOLID VISCOSITY. [BUM.. 94.

1600.

1400.

1200

1000

The specific resistance of petroleum is not so high as that of gasoline, though it is more than twenty 

times that of glass at 215°, and the 

insulationbreaks down less rapidly. 

The pressure coefficients decrease 

in marked degree with rise of temperature and nearly proportionally 

to it, and they actually pass from, 

positive to negative values. They 

are of a larger order of numerical 

magnitude than the glass coefficients. At 310°, where the petroleum coefficient is negative and the 

glass coefficient, according to Ta- 

» bles 48 and 50, positive, a criterion

 a of the effect of the oil is obtainable. 

& The .glass tube ! does not stand this

^

I test fully, since the pressure coeffiI cients of oil and glass in series ix

I are both negative, though the effect

& of the glass is a decided algebraic

=2 in crease of the oil coefficient. More-

| over, as the trustworthiness of a

 | tube like Fig. 14 reversed is no

| longer vouched for, I made the

 ^ remaining experiments with the

-g tube Fig. 16. I also tested a better

. I insulating oil.

I 101. Pressure coefficient of thin 

§ machine oil. Tables 53 and 54

<0

| contain data for the insulation and 

. ^ resistance of thin mineral machine 

° oil ("mineral sperm"), and also for 

£ glass surrounded by it. At 215° 

the resistance of the liquid is more 

than 50 times that of glass, and 

the breakdown in the former case 

much less rapid. Two glass tubes 

of the form Fig. 16 were used consecutively. In the first of these 

the inte. jal and external diameters 

of the inner tube were 0-24 and

800 \

;eoo

400

,-100

-200

/-300.

 400

1 1 strongly suspect that some oil had worked 

itself down into the sodium amalgam, and that 

this is the true cause of the exceptional behavior 

referred to in the text. This inference was sustained by a dissection of the tube after the experiment.
BAKUS. ] PRESSURE COEFFICIENT OF OILS AND GLASS. 121

Q.34 centimeters, respectively; in the other the dimensions of the 

inner tube were those given in § 87.

TABLE 53. Insulation and pressure coefficient of thin mineral machine oil. 

[ p0=150 atm. Ill sulation at 20°, 3 X KPio. ]

Scries No. 

0 

K 

Meanfo-XlO6

5.

215°.

320X106 w

+960.

5. 

*215.

110X10Bw

 440.

X10S 

6R/JR

400

400

 220 

-160

 190

dp

410

420

410 

430

440

fo-XlO6

970

960

 525 

-370

 430

Scries No. 

0

E

Mean fcrXlO6

5.

1 310°.

50X106w

+300.

10'X 

<5K/R

95

95

14.0

125 

400 

" 400

Sp

370

340

400

390 

410 

420

fc-XlO8

+260

280

350

320 

970

two

* Dirty, after an explosion. t Clean, refilled.

TABLE 54. Pressure coefficient of glass, surrounded ly mineral machine oil.

[2?0 = 150 atm.]

Series No.

8 

R,

Mean fcrXlO6

XI.

215°.

80X103o»

+138.

XI.

215°.

120X103o>

+143

XI.

310°.

e exio^ to

t 8X103 w

+117.

10' X 

«R/R

61

59

53

67

41

48

46

52 

49

48

&p

445

420

425

420

363

415

420

410 

420

415

fe-XlO6

137

140

127

157

115

116

112

126 

117

115

Series No.

e

K

Mean fc,-X106

XI.

215°.

190Xl03o>

+145.

XI.

100°.

30X106 w

+250.

*xn.

215°.

360X10»u

+173.

*X1I.

310°

26XlO'o>

+168.

10:i X 

8K/E .

57

59

71

04

113

CO

69

63

54

CO

67

$

400

400

385

-365

375

395

395

355

350

350

380

fcrXlO6

' 143

147

185

260

300

170

175

175

155

170

180

. *Anotlier tube of higher resistance.

Some of these results are shown in Fig. 21.

Eepetitions of this work.led to virtually the same uniformity of result, as is well evidenced by the close coincidence of the data for 215°. 

The coefficients of the two tubes, however, are not identical. A feature 

of Table 53 is the change of sign of the pressure coefficient when the 

oil has become contaminated. It is in these experiments (Table 53)
122 THE MECHANISM OF SOLID VISCOSITY. [BULL. 94.

that I specially observed the apparent accommodation detailed in § 121. 

As a whole, the data are in reasonable conformity with Table 48.

102. Pressure coefficient of thick machine oil. My final experiments 

were made with a A^ery sticky mineral machine-oil (cf. § 83). Two 

tubes of the form Fig. 16, but of different resistances, were used (§ 101).

100" ZOO^ 300

FIG. 21. Pressure coefficient and temperature for thin mini

era! machine oil and for glass.

At 310° the oil coefficients are negative, whereas the glass.coefficients 

remain distinctly positive: This seems to be a conclusive test, since 

an effect of the glass in changing the sign, or in anyway increasing 

the oil coefficients is inconceivable. The increase of the latter with 

pressure at 215° (cf. Table 55) is probably an actual occurrence. The 

two tubes again differ in their properties.
feARUS. ' PRESSURE COEFFICIENTS OF OILS AND GLASS. 123

TABLE 55. Insulation and pressure coefficient of sticky mineral machine oil. 

[p0=150 atm. Pressure coefficient of glass. Oil insulation at 100°, 4X 10;'<o.]

Series No.

e

E

MeanfcrXlO0

0.

215°.

130X106<o

+510.

6.

310°. 

18X10"a> 

 290.

10' X

<5E/E

530

520

125

155

-140 

 145 

 120 

-125 

-125 

-115

&p

810

820

360

400

440 

410 

420 

450 

470 

430

fcrX10B

C55

035

350

390

 320 

 355 

 285 

 280 

 205 

 270

© 

Tube of low resistance inserted.

xin.

100°.

UX10"u>

+135.

52

64

115

99

415

420

820

810

125

150

140

125

Series No.

e

E

MeanfcrXlO6

xin.

*215,

120X103 o>

129.

103 x 

5E/E

73

42

50

Sp

430

450

400

fcrX10°

170

92

125

Tube broken.

Tube of high resistance inserted.

XIV. 

215°. 

730X103 w

+205.

XIV. 

310°. 

36X103u>

+155.

81 

84 

1G5 

180

70 

60 

130

125

54

400 

420 

830 

830

415 

420 

.820

780

400

202 

200 

200 

220

170 

145 

1.60

100

135

* Dirty after an explosion.

These results are shown in Fig. 22.

103. Digest. In Tables 56 and 57 I have briefly summarized the statistics of insulation for oil and for glass. ^ All reference is made to 215°, 

since these measurements are the more reliable. The table is not intended to convey more than a mere estimate of the conditions encountered.

TABLE 56. Breakdown of resistance in the case of the divers oils examined.

o

Sperm 

oil.

3X106

60

7

1

Gasoline.

1800X10°

10

2

1

1

Petroleum.

400 X106

20

1

 0

Thin 

mineral 

machine 

oil.

1000X10"

300 '

30

1

.K

Very thick 

mineral 

machine 

oil.

19flfi V1A6

QA

i

 i

TABLE 57. Brealcdoion of resistance in the case of divers glass arrangements. 

[Specific resistance at 215°, 19X106 .!

Glass in 

o 

100

215

310

Sperm oil.

500

1

Gasoline. Petroleum.

1400

1

 2

Thin 

mineral 

machine oil.

300

1

 2

Thick 

mineral 

machine oil.

1

 fis
124 THE MECHANISM OF SOLID VISCOSITY. 

DEDUCTIONS.

[BULL. 94.

104. Effect of pressure. It appears, from Table 48 et seq., that the 

pressure-coefficient does-not decrease with the size of the pressure interval dp. The tendency is rather iu favor of an increase j but this is 

obscure. Hence the results obtained are properties of either the oil 

or of the glass, and not incidental disturbances. Moreover, I am war-

. 22. Pressure coefficient and temperture for 

thick mineral machine oil and for glass.

ranted in taking the means of the divers pressure coefficients found at 

any temperature as the probable value at that temperature.

105. Temporary and permanent effects. Remarks on the discrimination of temporary and permanent effects have been made in §§ 95, 97.
BARUS.] PRESSURE COEFFICIENTS OF OILS AND GLASS. * 125

106. Chart. In order to obtain a clear insight into the data of Tables 

48 to 55, it is best to construct pressure coefficient as a function of temperature. This has been done in Figs. 18 to 22, above. It would be 

more in keeping with the present work to coordinate this coefficient 

with resistance; but the latter data are not sufficiently accurate.

107. Pressure and, chemical equilibrium. Turning attention first to 

the behavior of the solid insulator, it appears that the electrical resistance of glass increases in very marked degree with the pressure which 

is brought to bear on it. In my earlier paper1 , in which I subjected 

glass to tensile stress (presumably dilatational), I found that the resistance had pronouncedly decreased. I also found that the results at 

360° were not as evident as at 100°. Hence the present and the earlier 

observations, though attacking the question from opposite points of 

view, are in accord. I am thus justified in announcing that the chemi. 

cal equilibrium of a solid changes ivith each change of strain (§ 114)..

108. Effect of temperature. The tables further show that the pressure coefficient of resistance decreases with rise of temperature; or that 

the effect of pressure decreases algebraically as the number of free ions 

available for the transfer of charges become greater. In an earlier 

paper2 1 showed that the resistance of a liquid electrolyte like zinc sulphate in water, or of a liquid metal like mercury, is a decrease of specific resistance. Finally, the present results for insulating oils contain 

several examples in which a passage of the positive into the negative 

pressure coefficient is directly observed. I conclude that the curve for 

glass, if prolonged, will eventually intersect the axis of temperature 

somewhere in the region of low red heat, and that the further course 

will be negative. Hence for all substances, solid or liquid, there is a 

point or state of electrolytic dissociation at which the effect of pressure 

on resistance is nil, or at which the increased molecular stability obtained by pushing the molecules nearer together, and perhaps of binding the constituents of the individual molecule more firmly together, 

counterbalances the decrease of the path over which the ion travels in 

conveying charge. Taking all the results for glass, oils, the solution, 

and the metal into account, it appears that the complete functionality 

will be given by a curve which is asymptotic both to the vertical in 

the region of low temperatures and positive pressure coefficients, and. 

to the horizontal in the region of relatively high temperatures and neg- ' 

ative pressure coefficients; The nature of this curve I have not been 

able to work out (§ 100), nor will it be the same for all substances.

109. Molecular effects of stress. Having thus found a consistent behaviour in metals and electrolytes in relation to strain, I am prepared 

to accept the proposition italicized in § 107 as true for solids3 generally.

1 American Journal of Science (1889), vol. 37, p. 349.

2 American Journal of Science (1890), vol. 40, p. 219.

3 To my knowledge the only experiments on the efl'eet of pressure on the resistance of solid metals 

nro due to Cliwolsou (Carl's Kepertoriuni, vol, 14, p. 26, 1878,) who 8ho\ya that their pressure coolQclont, like that of mercury, is negative.
126 ' THE MECHANISM OF SOLID VISCOSITY. [BULL.94.

For the case of metals Osmond1 has partially anticipated me, stating 

that strain more or less completely converts cold metals from one definite molecular condition into another. I have been unable to find, 

however, that Osmond has any direct evidence to support this assertion, and I have already pointed out 2 some of the difficulties which Osmond must surmount before his view can gain general credence. If 

mechanical stress is to convert «-iron into /?-iron, it is not to be overlooked that whereas the hardness called temper changes the electrical 

resistance of steel enormously (as much as 300 to 400 per cent), the 

electrical eifect of mechanical strain is relatively negligible. Even 

though much of this discrepancy can be explained away, direct experiments on metals confirming Osmond's view'will not be easily forthcoming. Two years ago I spent much time in endeavoring to throw 

light on the polymerization of metals, by studying the hydroelectrics 

of stretched and soft wires3 , by dissolving hard-drawn and annealed 

iron, by investigating the carburation changes of strained steel; but 

in no case have I found evidence of an indisputable bearing on the 

point at issue. .Finally, regarding the mere statement4 of inferences 

of the above kind, I believe I anticipated Osmond by interpreting viscosity in solids 4 with reference to Clausius's theory of electrolysis.

110. Hysteresis. The proposition of § 107, taken in connection with 

my observation of the occurrence of volume lag5, under isothermal conditions, suggests important inferences on the behavior of stress solids 

generally, and leads naturally to an explanation of hysteresis. If the 

pressure under which a liquid just solidifies, cseteris paribus, is in excess 

of the (positive or negative) external pressure at which it again liquefies 

(volume-lag 6 ), and if the chemical equilibrium of the solid acted on 

changes with each change of strain, then, quite apart from consider1 Osmond: Ann. dcs Mines, July-August, 1888, p. 0; M6m. de 1'artillerie de la marine (Paris, 1888), 

p. 4. Of course I make no reference against the ingenious experiments from which Osmond infers the 

spontaneous conversion of a-iron into /3-iron at red heat.

2 Nature, vol. 41, 1890, p. 370.

3 American Chemical Journal, vol. 12 (1890), page 1.

4 Am. Jour. Sci., -vol. 33, 1887, p. 28,

8 Am. Jour. Sci., vol. 38, 1889, p. 408.

 A good example of the volume-lag is given by an undercooled liquid like fused thymol (melting at 

53°), for ins'tance, which at, say, 30° solidifies under about 500 atm., and does not again liquefy on removing the external pressure. I have worked with para-tolnidine, naphthalene, a-naphthol, paraffin, 

and caprinic, palmitic, and monochloracetic acids. My original belief in the general character of 

these static phenomena has recently been disturbed by new experiments, in which I found for the 

special case of paraffin that it would be possible to be misled by local solidifications of the column 

under pressure. The volume-lag is always marked when there is even a suggestion of undercooling. 

The action of pressure is then similar to the closing of a door and opening it again without lifting the 

latch. Observations made at intervals of 20 minutes each, with palmitic acid, showed that at 60° this 

substance solidifies between 300 and 400 atm., and then remains solid even between 200 and 300 atm. 

At 100°, a-naphthol solidifies at 000 to COO atm., and when pressure is being removed it remains solid 

until about 150 atm. Undercooled caprinic acid at 20° solidifies under 150 atm., remaining solid. At33° it solidifies at about 500 atm., and then fuses again at about 200 atm. Local solidifications here 

suggest the occurrence of isomers or other impurity. Sometimes, as in the case of naphthalene, the 

volume-lag is not thoroughly static, but becomes viscous in character, etc. I have yet to study the 

effect of temperature on the, magnitude of the volume-lag, i. e., on the difference of pressures isothermally corresponding to solidification and to fusion. Very large pressure-intervals are esseptia) 

fpr this purpose.
HYSTERESIS. 127

ations directly involving the second law of thermodynamics, quite 

apart from the energy dissipated in the cycle, the solid at identical 

stress points needs not to be in the same chemical condition while 

stress is being removed in which it was when stress was being applied; for there will be certain groups of particles, uniformly distributed throughout the solid, which during the "stress-on" phase pass 

from a first molecular condition to a second, and which, in virtue of 

the volume-lag, do not regain their original state at identical pressures 

of the "stress-off" phase. The march in the two cases is not a symmetrical one. This I take to be the inherent nature of the phenomena 

studied by Conn1., Warburg3 , and others, and to which Ewing3, after 

much original research, has given the generic name hysteresis. In my 

note I pointed out the important bearing of the volume-lag on the molecular behavior of matter4 , though I have yet to specify my views in 

detail. The occurrence of hysteresis therefore implies a favorable 

molecular mechanism of the kind indicated, and one would not expect 

to find it at once in all substances.

Conformably with the above, the interpretation given by Mr. C. A. 

Cams-Wilson5 of his important discovery (to which I alluded in a 

former paper) is much more than an analogy.

111. Magnetic hysteresis. Warburg and Ewing have proved that 

hysteresis is not only associated with mechanical stress, but may be 

very clearly evoked by magnetic stress. Curiously enough, the evidence in favor of the views expressed in § 26 is here directly forthcom- 

 ing. Keinsen's6 discovery of the chemical influence of the magnetic 

field, additionally substantiated as it now is by the ingenious experiments of Bowland and Bell7, proves beyond a doubt that magnetic iron 

is more electro-negative than unmagnetic iron. Conformably with the 

above paragraphs, I therefore infer that this phenomenon is to be interpreted as directly evidencing a chemical difference between magnetic 

and unmagnetic iron, and as such I consider it an exceedingly important step towards an ion theory of magnetism8 . Thus the occurrence

'E. Cohn: Wied. Ann., vol. 0, 1878, p. 388.

2 Warburg: Wied. Aim., vol. 13, 1881, p. 141.

3 Ewing: Phil. Trans., vol. 2, 1885, p. 545.

4 Am. Jour. Sci., vol. 38, 1889, p. 408.

8 Cams-Wilson: Phil. Mag., vol. 29, 1890, p. 200.

6 Eomseii: Am. Choni. Jour., vol. 3, 1881, p. 157.

'Kowlandand Bell: Phil. Mag. [5], vol. 2C, 1888, p. 105.

"In Nature (vol. 41, 1890, p. 370) I pointed out tlr.it closed helical paths of molecular dimensions, 

each consisting of a right and a loft hand screw-thread, with their ends joined, can bo generated hy 

the symmetrical interpouetration of two congruent Bravais nets. I inferred that electrical charges . 

urged along and around the. said closed helical paths by the action of the magnetic field could be nmdo 

to replace the nsual conception of molecular currents circulating in a molecule without resistance. 

IFrom this point of view magnetic and electric fields merely differ in the rotational character of the 

former as compared with the nonrotational character of %he latter. AVhcrcas in an electrolyte the 

ion-dissociation takes place as the result of chemical relations and heat, it takes place in a inetnl under 

the more influence of heat. The immediate action of both fields is directional; and by taking advantage of the positions of labile equilibrium of the ion, they act in a way analogous to Clerk-Maxwell's
128 THE MECHANISM OF SOLID VISCOSITY. JBULL.94.

of tlie chemical difference in question, and the explanation of magnetic 

hysteresis, as given in the present and preceding paragraphs, mutually 

sustain each other.

112. Mechanism of viscosity. Whether viscosity and dissociation in 

solids are to be explained with reference to a single mechanism, or, 

whether we are to conceive of two mechanisms (molecular and atomic 

frameworks), one, as it were, Avithin the other, is at the present stage 

of research a mere question of special convenience. The remarkably 

low viscosity at the yield-points of metals, as well as the similarly low 

viscosity near the Gore-Barretfcphenomena, are both in conformity with 

the sudden passage from a first molecular state to a second^ through an 

instability.

It may be well to point out the bearing of the singular minimum1 of 

the viscosity of hot iron on the interpretation given of Maxwell's theory,2 

more explicitly. When iron passes through Barrett's temperature of 

recalescence, its molecular condition is for an instant almost chaotic. 

This has now been abundantly proved.3 The number of unstable configurations, or, more clearly, the number of configurations made unstable 

because they are built up of disintegrating molecules, is therefore at a 

maximum. It follows that the viscosity of the metal must pass through 

a minimum. Physically considered the case'is entirely analogous to 

that of glass-hard steel suddenly exposed to 300°. If all the molecules 

passed from Osmond's ft to his a state together, the iron or steel would 

necessarily be liquid. This extreme possibility is, however, at variance 

with the well-known principles of chemical kinetics. The ratio of stable' 

to unstable configurations can not at any instant be zero. Hence the 

 minimum viscosity in question, however relatively low, may yet be large 

in value as compared with the liquid state.

In a preceding bulletin (No. 73) I have shown that to explain the varied 

physical phenomena which accompany temper, it is sufficient to recognize 

some special instability in the tempered metal. This condition is given 

by the carbide configuration, and the physical explanations in question 

may be made without specifying its nature further. The essentially 

chemical nature of this phenomenon is, however, not to be ignored. 

Seeing that the amount of carbon contained in steel is not large, the 

electrical resistance of hard steel is at once an expression of its chemdemoiis ("Heat," chap, xxn, § 10), producing marked effects at the expenditure of a relatively small 

amount of work.

The advantage which I seek for in this tentative suggestion has direct reference to my own line of 

work. I can picture to myself the role played by ilia foreign ingredient chemically present in iron, in 

modifying the retentiveness and the magnetic stability of the metal. Thus I conceive' tbe carbon 

atoms in hard steel to be so placed that after magnetization they block out definite closed helical paths 

in the metal, along which the transfer of charges must thereafter take place. Hence an increase of 

magnetic stability as contrasted with pure iron, where from any point four or more such paths may 

be open. Again, other substances (manganese, say) may be conceived to unite with the iron in such 

a way as to shut out the possibility of closed helical paths altogether. The fact that my permanent 

magnet is essentially a self-exhausting engine does not seem to be a serious objection.

1 Roberts Austin: Nature, vol. 41,1890, pp. 11,34.

"Barus: Bulletin, TJ. S. Geol. Sur., No. 73,1891.

* C£ John Hopkinson: Phil. Trans., London, vol. 180, p. 443, 1889, where the literature may be fomi<|.
VISCOSITY AND ELECTROLYSIS. 129

ical composition, structurally unknown though it be. Hence in the 

electrical diagram of the phenomena of temper, constructed by Dr. 

Strouhal and myself,1 the time variations of resistance of hard steel at 

any given temperature may be interpreted as a case of Wilhelmy's2 rate 

of chemical reaction, and expressed in accordance with his well-known 

exponential law. This indeed is the character of the observed curves. 

Hence also the full diagram of the phenomena of temper, considered 

both in their variation with time and with temperature, is available for 

the elucidation of moot points relative to the effect of temperature on 

rate of chemical reaction.

From all that has been said it is clear that the mechanisms of viscosity 

and of diffusion (electrolysis), though containing a similar thermal 

factor, can not be quite the same. Thus it has lately been shown by 

Reformatsky 3 that the speed of the same reaction in a jelly and in a 

water medium do not appreciably differ. On the other hand diffusion 

in solids is essentially a slow process. Studying the colored oxide 

coats on iron. Dr. Strouhal 4 and I pointed out that the outer surface 

of the film is oxidized as highly as possible in air; and that the inner 

surface of the film, continually in contact with iron, is reduced as far 

as possible. This distribution of the degree of oxidation along the 

normal to the layer, is equivalent to a force in virtue of which oxide is 

moved through the layer, from its external surface to its internal surface. The formation of an oxide coat is thus a case of diffusion. Conformably with this view, the film, during its formation, behaves like an 

electrolyte, as was discovered and substantiated by Franz, Gangain, and 

Jenkin, and more recently by Bidwell and by S. P. Thompson. We then 

adverted to the crucial difference between diffusion in solids and diffusion in liquids, inasmuch as in the former case (solids) diffusion demonstrably ceases after a certain small thickness is permeated. The limit 

thickness of the film is reached asymptotically through infinite time. 

It has a definite value for each temperature, increasing as temperature 

increases. In the light of other information since gained this explanation is substantiated. The formation of the oxide coat is a case of solid 

diffusion, and as such it bears the same relation to the diffusion of 

liquids that the viscosity of solids bears to the viscosity of liquids. 

The two phases (solid, liquid) of each phenomenon are to be correlated 

in ways essentially alike. The available stress, as compared with the 

available instability, determines the time character of the result.

To recapitulate: In the usual cases of viscosity there are presented 

to us cases of localized destructions of configurations, the integrant 

parts of which are stable molecules. In the case of chemical interaction between contiguous configuration (diffusion, electrolysis) consist1 Bulletin, U. S. Geol. Sur., No. 14, chapter n, 1885.

2 Wilholmy: Pogg. Ann., vol. 81,1850, pp. 413,499.

3 lleformatsky: Zeitschr. f. phys. chera., vol. 7, 1891, p. 34. 

«Bull. TT. S. Geol. Sur., No. 27, 1880, p. 51.

Bull 94 9
130 THE MECHANISM OF SOLID VISCOSITY. [BUI.L.M.

ing either of an exchange of atoms or of molecules, there need be no 

viscous effect, provided the exchange is perfectly reciprocal. In the 

case of irreciprocal interaction, finally, by which molecules are left in 

the lurch and broken up, the configuration of molecules will also be 

modified, and hence a viscous effect appears. Examples of all these 

cases are frequent in the above text.

113. Electrical effects of ceolotropic stress. It follows from tables 48 

to 55, that in an seolotropically strained transparent solid like glass, electric conduction is different in different directions, the difference depending on the intensity of strain. Suppose this be considered in connection with the doubly refracting property of such a solid, and again 

with Warburg and Tegetmeier's 1 researches on the electric conduction 

of quartz along its optic axis, with nonconductiou at right angles to it. 

Then the inference is tenable, that the strain artificially sustained in 

one case is naturally sustained in the other. 'Tegetmeier's conducting 

sodic silicate, ingrained in the crystalline structure of quartz, and possessing larger molecular conductivity in quartz than in glass, may be 

looked to as responding to strain of the kind suggested.

UNAVOIDABLE ERROftS.

114. Polarization. In the next six paragraphs it will be convenient 

to discuss some of the errors relating to both the measurements of resistance and electromotive force.

The effect of pressure on the polarization occurring in case of the 

above cell and of exceedingly weak currents is somewhat difficult to 

handle. Warburg2 and others have shown that the reaction is essentially Na/glass/Hg changing to Na IsTazSiOsglass/NaHg, or a mere 

transfer of sodium through the walls of the glass, by aid of sodium 

silicate as a conveyancer. I shall therefore have to rely on the data of 

Table 49, in which, if a marked effect of pressure 011 polarization had 

been present, it would have been detected. It will be remembered that 

I commenced with high initial pressures (jp0=50 to 200 atm.) to obviate 

incidental disturbances.

115. Insulators. The effect of pressure on the oil in the piezometer 

was specially investigated in each case. Cf. Tables 50 to 55, § 122.

116. Shifting isothermal planes. A source of error is introduced by 

the temporary shifting of the isothermal planes of the piezometer, 

during compression, in virtue of the compressibility of the oil contained 

in the tube. Adiabatic thermal changes during compression or removal 

of pressure would produce effects of a sign opposite to those of the 

tables.

To remove both of these it was often my habit to wait 3 to 5 minutes,

'Warburg and Tegotmeier: \Vied. Ann., vol. 35, 1888, p. 455; vol.41, 1890, p. 18. 

"Warburg: Wied. Ann., vol. 21, 1884, p. 622 j vol. 35, 1888, p. 455.
BARUS.] UNAVOIDABLE ERRORS. 131

supposing the original thermal state was then nearly enough regained. 

Longer waiting was not safe because of fluctuations of the astatic system of the galvanometer.

Special tests were made as follows : In Fig. 23 let P Q be the piezometer closed at Q, and receiving pressure in the direction of the arrow. 

Let A B be the position of the glass resistance tube. Finally, let the 

hollow cylindrical vapor bath surrounding the piezometer stretch respectively from & to d, or from a to c, or from c to e. Parts lying within 

the vapor bath have constant temperature, which falls off rapidly 

from both ends of the bath towards the ends of the piezometer. When 

pressure is applied the vertical isothermal planes of the compressible 

oil are all moved from P to Q. With the vapor bath in the position 

1} d. pressure would thus cool the end A and heat the end B of the glass 

tube AB; but the cooling would exceed the heating. Hence an error 

of the sign of the data, Table I, etc. Now let the vapor bath be 

shifted to the position a c and the thermal state be steady. The B-half 

of the tube A B is now exposed to cold, and compression can only have 

the effect of heating these parts, seeing that the A-half is protected.

CL c c\ e

V & Q

CL & c

Fio. 23 Diagram.

Hence an error of a sign opposite to the data of Table 48, etc. Finally, 

when the bath has the position ce, the error first considered would be 

accentuated.

I made experiments in accordance with this scheme at 310°, bnt 

found that this severe test did not change the character of the results 

of Table 48. Data are superfluous. Again, decreasing the length of 

the tube A B had no appreciable effect. Similar tests were made with 

reference to Table 49.

117. Electromotive force. It is clear at the outset, since pressure increases both the resistance of glass and the electromotive force NaHg/ 

glass/Hg, that changes of the latter will act in a way tending to wipe 

out the change of resistance. Let e, I, E denote the electromotive force, 

current, and. resistance of the uncompressed circuit. Let Ip be the current corresponding to pressure p, and 7cR and le, be, respectively, the 

pressure-coefficients of resistance and electromotive force. Then

,. ...... (1)

Table 49 gives fc(,=10'10B , say, whence the values of Table 58 result 

from Table 48, series ill (cf. § 95). In the final column fc'R = £R/R . dp, 

the former coefficient.
132 THE MECHANISM OF SOLID VISCOSITY. 

TABLE 58. Allowance for increments of electromotive force.

[0 = 215°.]

[nULL.94.

P

523

995

1411

512

1016

1403

103^ . ke

5.2

9-9

14-1

' 5-1

10-2

14-0-

Kl-hPfe)

21-18

21-28

21-37

21-18

21-28

21-37

IP

19-47

18-11

17-27

19-39

18-07

17-28

lOexM

168

17!)

108

180

172

109

IPX**

157

164

156

109

163

156

Thus the data underlying §§ 10G, 107,108 are accentuated. At 310° 

a permanent pressure-coefficient Jce could not be detected, and at 100° 

it is certainly very much in error (§ 118). Since therefore kc is never 

fully vouched for, I have omitted it in the computation of 7<;R altogether.

118. Short circuiting. In case of an uncompressed circuit shunted by 

unavoidable leaks, let EI, E2, E3 be the resistances of the cell, the shunt, 

and the metallic circuit respectively. Similarly let i^ i-2, i3 be the three 

partial currents corresponding respectively to EI, E2 , E3 . Let tfEi/Et 

be the effect of pressure on the resistance of the cell (resistance tube), 

and de/e be the simultaneous increment of electromotive force. Fin ally, 

in case of the compressed circuit, let accentuated symbols replace the 

symbols for the uncompressed cell. Then a somewhat tedious reduction 

leads to

,-r, _

]/ l (2)

(3)

where (yE|/E1 =w^E2/E2/ and <?E2 /E2 is the pressure coefficient of the 

oil through which the leakage obviously takes place. Eegardin g tfE, /Ej 

in (2), if the resistance, E3, of the metallic circuit is relatively small, or 

if E! be reasonably small relative to the leak E2, the considerations of 

§ 111 at once apply. The case of $e/e, however, is serious. Supposing, 

again, that E3/Ei and Ely/E2 are small, the last equation reverts to

and thus the changes of resistance due to pressure are interpreted as 

changes of electromotive force. Zero or even electrometric methods 

will only measure the difference of potential of two points of the leakshunted circuit. Hence the permanent pressure coefficients (Seje) of 

Table 49 can not but be regarded with suspicion, and they are merely 

an essential justification of Table 48 et seq.

119. A final difficulty in case of short circuiting is not to be lost sight 

of. A leak usually includes an electrolyte between two different 

metals, and thus introduces an electromotive force in a way quite beyond computation.

120. Electromotive force and pressure. The consideration of the data
ELECTRIC RESISTANCE OSCILLATING WITH PRESSURE. 133

of Table 40 would now be in order; but for the reasons just stated I 

hold the work scarcely ripe for discussion, and will therefore withhold 

remarks until 1 can devise some more nearly faultless method of measurement.

121. Graphic representation. In order to exhibit the full character of 

the individual observations of Tables 48 to 55, I shall discuss a series 

of data which I Avas first inclined to interpret as an electrical manifestation of volume " accommodation" (§ 101). In Fig. 24, A, B, C, the obfiOO

.FIG. 24. A, B, C: Chfirts showing tlie oscillation of t,ho, electric conductivity of glass with pressure 

at, 215°, 310°, and again at 215° respectively. Experiments made consecutively. D, E: Charts 

.showing the oscillation of the electric conductivity of very vicious hydrocarbon oil ("mineral 

machine oil") with pressure, at 215° and 315° respectively.

served intensities of current in relative measure are given as ordinates. 

They are therefore inversely proportional to the resistance of the glass. 

The abscissae are times, supposing that the times consumed in making 

each triplet of observations are equal and similar. The oscillations are 

due to the fact that pressure is raised from about 150 atmospheres to 

about 000 atmospheres, and then lowered to the first value again, thus 

giving the three points for each of the triplets numbered.
134 THE MECHANISM OF SOLID VISCOSITY. IB* ,L.04.

In Fig. 24, D, E, similar results are given for thick mineral machine 

oil. In the former, pressure was twice increased from about 160 to 080 

atmospheres and back again; and then from about 160 to 540 atmospheres, thus obtaining amplitudes of different values. In E pressure 

oscillated between about 150 and 600 atmospheres.

A, B, 0, which were obtained consecutively, show a gradual decrease 

of resistance to a limit, very obviously in A at 215°, quite as obviously 

in B at 310°, but not obviously, if at all, in. C. Hence the inference is 

suggested that the continued exposure to strain alternations at 310° 

has wiped out all viscous instability possible at 215°. The volume 

elasticity of the glass, so far as its chemical manifestations are concerned, is now constant. The objections to this interpretation are 

twofold. In the first place the amplitudes of oscillation are constant 

throughout, caet. par., and do not converge to a limit. Again, the results 

for oil show similar phenomena, not very obviously in D, but marked 

in E, where both the negative pressure coefficient and the resistance 

decrease act together to invert the figure.

122. Electric instability of hydrocarbon oils. I have finally to refer to 

the results obtained with highly-insulating liquids. It appears from 

these that the effect on resistance of an additional number of molecules 

splitting up in consequence of the removal of a fixed amount of pressure, decreases rapidly with the total number splitting up, where the 

decrease is to be taken in an algebraic sense and to include a march 

through zero. In the case of sperm oil, gasoline, petroleum, thin and 

thick hydrocarbon machine oil, the observed pressure coefficients pass 

from positive towards or actually into negative values as temperature 

increases, and at a rate which for the same oil between 20° and 300° is 

nearly constant.

These rates (<SB/R. dp. 66} are as follows:

TABLE 59. Rate of thermal variation of pressure coefficient.

Sperm oil.

 3/108

Gasoline.

 9/106

Petroleum.

- 6/105 

 10.10"

Thin mineral 

machine oil.

 7/106

Thick mineral 

machine oil.

 6/106

The figures therefore denote the change of the pressure coefficient 

per degree centigrade. In a general way it may be noted that this 

change is least in sperm oil, where ions are present in greatest number.

Similar remarks were made in my earlier paper 1 , after an examination of mercury and solution of zinc sulphate. Both coefficients in this 

case were negative, and I was not prepared for the positive coefficients 

(tfR/B.<?p) so marked in the present paper. The data as a whole, 

therefore, show that it is not permissible to pass from one substance 

to another; doubtless because the number of molecules which must

1 Am. Jour. Sci., vol. 40, 1890 p. 222-
BABUS.] CONCLUSION. 135

split up per unit of area to discharge the field varies largely from substance to substance. Inferences are to be drawn from one and the 

same solvent, either electrolytically dissociated by temperature, or 

modified by the solution of some given substance, or both.

123. The remarks of § 122 are substantiated by the incidental results 

of Table 53^ where the number of ions is increased by dissolved dirt. 

It agrees with the negative pressure coefficient found for zinc sulphate 

(loc. cit.). Moreover, by keeping the thick machine oil at 310° for two or 

more hours, I found that its resistance continually decreased, while the 

pressure coefficient passed from indistinctly positive to pronounced 

negative values. Dissociation is here to be inferred.

I have only touched upon this question in passing; but if it can be 

proved that the occurrence of negative pressure coefficients is an index 

of solution, then metals may also be regarded as holding ions in solution. In general a sequence of changes of state or of molecule corresponding to gas-liquid, liquid-solid, may be regarded as crowded into 

the solid state, though the external manifestations are here no longer 

obvious at once.

124. Conclusion. The present research has been excessively tedious 

and elusive. Moreover the final values for the pressure coefficient of 

glass (Tables 54, 55), although consistent, do not show the uniformity 

of values which I had hoped to reach. Nevertheless the results are 

marked, and unless there be some occult behavior of polarization, I do 

not believe that I have been led astray in my inferences. In so far as 

my results are correct, they contain the first direct and connected evidence of the change of chemical equilibrium with strain.

Eegarding the behavior of liquid insulators like the hydrocarbon 

oils, the results found present many points of interest, and I have no 

doubt that a more systematic study of the subject than I have been 

able to make would throw much light on the details of the mechanism 

by which electricity is conveyed.

INDEX.

A.

Page.

^Eolotropy, electric effect of ____.- _. 130 

Annealing, motional....................30,32,38

Annealing, thermal......._ ...... 37

Annealing (secular), of steel... .. 74 

Apparatus for testing viscosity under 

strain .................................... 18

Apparatus for electrolyzing. glass, etc.81,82,86, 

88,90,97,110,111,112

Apparatus for measuring potentialized

energy. ... _ 10 

Apparatus for electrolyzing oil._..__ 113 

Auerbach on hardness .. ___.____ 27

B.

Bibliography of mechanical strains...... 17

Bibliography of electrical resistance of 

glass...............--.-....-.. ......... 85

Braim on molecular change ... _. _ 29 

Breakdown of resistance In oils and glass. 123 

Breakup, kinds of ...................._ 30

Bottomley, experiments of......... __ 75

C.

Carbon, how estimated......._._....41,44,46

Carburation affected by strain......... _ 40,42

Carburatiou, results for, discussed....... 44

Carus-Wilson, -views of...../..............72,127

Cohn on cyclic traction . _..._.._ _..A.. , 127

D.

Diffusion promotes solution.............. 58

Diffusion, mechanism of .................. 129

Drowne, views of.. .................... 40,61

* E.

Electromotive force changed by pres-. 

sure .....................................116,132

Energy potentialized in strains .....101,105,107

Equilibrium (chemical) ofsolids...___.__ 109 

Ewingon hysteresis_.._............126,127

G.

Galvanometer, adjustment for Thomson's........_..._...._............ 114

Gasoline, pressure electrics of...._._117,123

Glass, electrical resistance of.__...... 85,91

Glass, pressure electrics of..._ ........109,123

, H.

Pago. 

Hardness defined by Hertz..__...... 27

Helical paths for ions .....__........... 128

Hertz on hardness......_.....___ 27

Hydroelectric effect of strain, of magnetization __.__........._._.... 63

Hydroelectric effect of strain discussed.. 69,70 

Homogeneity of steel, how tested........ 75

Hysteresis .........................__..126,127

I.

Instability, electric, of hydrocarbon oils. 134 

Insulators of oil, electrics of.............. 130

Ion theory of metallic conduction........ 73

Ion theory of magnetization............127,128

M.

Magnetization, hydroelectric effect of... 63 

Magnetization, theory of................ 127,128

Maxwell's theory of viscosity.__.._ 17 

Mechanism of viscosity.......___ 128

Metallic conduction, ion theory of...._ 73

Molecular change, electrically studied .. 63

O.

Oils, pressure coefficient of electrics of.. 134 

Osmond, views of ................27,47,61,72,126

P.

Petroleum, pressure electrics of._.... 118,

120,122,123 

Polarization changed by pressure....... 130

Pressure, effect of, on electrolytic resistance._.............................._124,133

(

Q.

Qulncke, experiments of.._..._.__ 83 

R.

Recalescence ......_......__.._ 27

Remsen, experiments of....... _ *-..._... 63,1 £7

Residual viscosity ..............._...... 39

Resistance, electrical, of stressed glass.. 85,91 

Resistance, electrolytic, changed by

pressure ..._. _ __.__124,133 

Rowland, experiments of _. _._ _ 63,127

137
138 INDEX.

S.

Secular annealing of cold steel.____ 74 

Shunts, errors due to ......... 132

Solids, chemical equilibrium of .........109,125

Solution, method of measuring ...... _ 48

Solution, rate of.......................... 48,58

Solution, data for, of steel....__.... 49

Solution of steel, digest for............... 59,60

Sperm oil, pressure electrics of _ .115,117,123 

Strain, hydroelectric effect of ..._...... 63

Strained wires, viscosity of.__.._ 28,31 

Strains, mechanical, bibliography of .... 17

Strains, energy potentialized in ....101,105,107

Strouhal on temper. .......____79,129

T.

Temper related to viscosity ...... ____ 31

Theory of magnetization . ...._....127,128

Thomson, views of ... . 82,99

Pago. 

Torsion changes electrical resistance of

glass ..........................._....91,95,99

Traction, cyclic......._.._..._.._ 25

Traction changes electrical resistance of

glass....................................91,95,99

Twisting, cyclic............................ 33,37

V.

Viscosity, Maxwell's theory of._. ___ 17 

Viscosity of drawn wires.___..._.. 20,23 

Viscosity of stretched wires.............. 23,24

Viscosity of ejectrolyzing glass .._..... 80

Viscosity, mechanism of_...__.._ 128 

Volume lag, examples of _....___ 126

W.

Warburg electrolyzes glass __.._ 81,85 

Warbnrg on cyclic magnetization ....... 127

Wassmuth, experiments of __......_ 106