Bulletin No. 31O" B> Descriptive Geology, 122 

0, Underground Waters, 74

DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY

GEORGE OTIS SMITH, DIRECTOR

SUMMARY OF THE

CONTROLLING FACTORS OF 

ARTESIAN FLOWS

BY

MYRON L. FULLER

WASHINGTON

GOVERNMENT PRINTING OFFICE

1 9 0 8

CONTENTS.

j : Page.

I Introduction ____________._..___.. __________________ 7

; Underground conditions_______________________________ 8

| Underground reservoirs __________________________ S

J Types ____________________________________ S

: Original forms______________________________ 9

' Original pores_________________________ 9

j Lamination planes _____ - 9

Bedding planes _________________________.. 10

i Vesicles _________________________.____ 1.0

| Secondary forms____________________________ 11

Secondary pores ___________________________.. 11

Solution openings _______________________. 11

Mechanically formed reservoirs__________________ 12

Fracture openings ___________________________ 13

Irregular openings __________________ __ 13

Joints _________________________-_____ 13

Vein contacts_^___________________________ 1.4

Igneous contacts__________^_______________ 1.5

Faults _________________________.._______. 15

Shearing planes______________________________ 15

Cleavage planes___________________________ 15

Foliation and schistosity planes ____ __ 15

Sources of underground \vater__-_____________________ 15

: ; Waters from the atmosphere__________l________ _ 10

,:'' Precipitation and condensation_________,____ _ 10

Waters from lakes and streams-_____________ 1.7

Waters from the ocean______________ ______ 17

 , Contemporaneous absorption________________.__ 1.7

; Originally included sea water ________________ 18

| Waters from the rocks of the crust_________________ IS

I Chemically excluded waters _,_______________ 19

| Physically excluded waters ___________________ 19

j Waters from the centrosphere__________________ 19

j Confining agents. ______________________________ 20

} Bedded rocks.____________-_________________ 21

| Upper confining agents_____________________ 21

; Impervious bed__________________________ 21

j Stratification planes______________________ 21

; Friction_______________________________ 22

| Mineral crusts_: _______________..____ 23

Frost zones ____________________________ 23

Confined air and gas_____________________ 23

Fresh water________________________ 24

Sea waiter _______'_ __________________ 24
4 . CONTENTS,

Underground conditions Continued. 

Confining agents Continued.

Bedded rocks Continued. ' Page.

Lower confining agents______________________ 24

Cementation.:___._______________________ 25

Heat____________:______________,____ 25

Pressure______ . ____________________ 25

Jointed rocks__________ _________..__..______ 26

Upper confining agents________________________ 26

Impervious wall ______________________ 26

Impervious covering on surface_______________ 26

Frost fillings_________________'._______________ 26

Vein fillings ____________________________ 26

Weathering products___________________ 26

Sea water________________________ 27

Converging walls _________.._____________ 27

Interruptions of .joints _____________________ 27

 Lower confining agents________________________ 27

Nature of artesian circulation ___l_______________________ 27

Primary factor _______________________________ 28

Gravity_________________________________ 28

Modifying factors______________________________ 28

Factors mainly affecting pressure____________________ 29

Barometric variations _ _____;_________ 29

Temperature variations______'. ________________________ 29

Density of waters_________:__________________ 30

Variations due to temperature_1______________ 30

'Variations due to^dissolved salts_____________ 30

\ Variations due to suspended solids____________ 30

Height of adjacent water levels __________.____'__ 31

' Water table _________________________ 31

Neighboring water bodies, etc____:_'___:___'. ______ 31.

liock pressure _________________.____:____ 33

Factors mainly affecting water movements_____________ 33

Requisites of artesian flows________________________ 33

Objections to common requisites______________________ 34

Pervious stratum __________:_________________ 34

j Impervious bed below_____________ __ _ 34

i Impervious bed above_________________________ 35

I Inclination of beds_____________________________ 35

[ Outcrop of porous stratum______________________ 35

i Adequate rainfall___^________________________ 36

Points of escape __________________ ___ 36

Essentials of artesian flows __________________ ___ 36

Modifying factors_______________________________ 37

Typical artesian systems ____________________________ 37

Artesian basin______________________ _ ._ 38

Artesian slope__________________ 38

Unconfiued horizontal beds________ 39

Bedding planes _____________ 39

Solution passages _ _ 39

Frost or mineral crusts____ : 40

Vesicular trap._ 40
CONTENTS. 5

Requisites of artesian flows Continued.

Typical artesian systems Continued. Page.

Weathered rocks beneath clays______.______~______ 40

Jointed crystalline rocks_________________.______ 41

Basins fed by joints______________ __--_ _ __ 41

Joint waters confined by alliiviiim___ _ ___ 41

Joint waters confined by sea water-___________ _____'_ 42

Foliation planes _____________.____._________ 42

Fault and contact planes________ _ . - - 42

Index____________________________-____________________ 43
ILLUSTRATIONS,

. Page.

PLATE I. Artesian reservoirs: A, The bedding plane; spring emerging 

from bedding plane in limestone; B, Ramifying channels along 

bedding plane in limestone_____________________ 10 

II. Artesian reservoirs: A, Earthquake crack filled with sand dike,

between walls of clay ; B, Underground solution channel___ 12

III. Artesian reservoirs : Torsion cracks, due to folding_______ 12

IV. Artesian reservoirs: Sheet jointing_________________ 14

V. Artesian reservoirs: A, Horizontal joint's in granite; B, Joint

and fault breccia__________________i_______ 14.

VI. Artesian reservoirs: A, Solution channel on fault line; B,

Crushed zone on fault________________________ 1C 

VII. Artesian reservoirs: A, Schistosity planes; B, Cleavage planes. 16 

FIG. 1. Conditions governing movement of water away from streams or

lakes___________________________________ 17

2. Form of sand grains__________________________ 22

3. Arrangement of sand grains in stratified deposits__________ 22

4. Section of an artesian basin_______________________ 38

5. Section of an artesian slope_______________________ 38 

G. Conditions governing flow from uuconfined horizontal sands___ 39

7. Conditions of flow from horizontal bedding planes.________ 39

8. Conditions of flow from solution passages in limestone______ 39

9. Conditions of flow from beneath frozen zone or mineral crusts___ 40

10. Conditions of flow from vesicular trap_______________ 40

11. Conditions of flow from joints, etc., uuder impervious clays____' 40

12. Artesian conditions in jointed crystalline rocks______'. ______ 41

13. Conditions of flow in alluvial basins_________________._ 41

14. Confinement of water in joints by valley silts^___..___ 41

15. Action o^ salt water as a confining agent___________ 42

16. Conditions of flow from foliation and schistosity planes_____ 42

17. Possible conditions of flow from fault and contact planes ___ 42

6
SUMMARY OF THE CONTROLLING FACTORS OF 

ARTF.SIAN FLOWS.

By MYRON L. FULLER.

INTRODUCTION.

Every text-book on geology and every treatise on hydraulics or 

hydrology discusses the occurrence of artesian waters. Unfortunately, 

however, only the more simple conditions are usually considered. 

The principle expressed by the widely prevalent maxim, " water 

seeks its own level," is readily grasped by every one, but it does not 

explain all of the features of artesian flows. That nature does not 

always do its work in the simplest way is recognized in all sciences, 

in none more generally recognized than in geology or hydrology. 

The ideal conditions shown in the text-books and treatises are often 

absent; while, on the other hand, flows occur under a great variety 

of conditions not commonly recognized and rarely described. The 

ever-present basin of popular discussions does not even predominate 

among the many types of artesian systems encountered in the field, 

and even the sloping bed is not essential. On the other hand, fissures 

and solution passages play very important parts, even in stratified 

rocks.

.For these reasons and because of the present activity in artesian 

investigations, but more especially because of the notable change in 

the use of tho term " artesian " since the publication in 1885 of the 

admirable paper of Prof. T. C. Chamber]in on the "Requisite and 

qualifying conditions of artesian wells," a it has seemed desirable to 

point out certain needed modifications to the postulated requisites of 

flow. No attempt at exhaustive treatment is made, the aim being 

simply to call attention to a few of the commonly neglected elements 

of the problem.

In view7 of the number of different senses in which the term 

artesian has been used in the past it will not be out of place to state 

that in the present paper the term is applied in the sense adopted 

by the United States Geological Survey after consultation with

« Fifth Ann. Kept. TJ. S. Geol. Survey, 1885, pp. 125-173.
8 CONTROLLING FACTORS OF ARTESIAN FLOWS.

leading geologists of the country, namely, to designate the hydrostatic 

principle by which confined waters tend to rise in virtue of the 

pressure of the overlying water column, whether or not this pressure 

is sufficient to lift the water to the surface and produce a flow.*

UNDERGROUND CONDITIONS.

Preliminary to the discussion of the essential factors of artesian 

flow, a resume of the geologic conditions affecting artesian waters is 

desirable. The following paragraphs present some of the factors 

bearing on the occurrence and movements of such waters.

UNDERGROUND RESERVOIRS. 

TFPES.

By " underground reservoir " is meant the opening 'or system of 

openings in which underground water is contained. It is needless to 

say that, except an occasional cavern of very limited extent, such 

reservoirs bear no relation to open basins of the surface type, but are 

most of them rock strata or masses in which the only openings are 

spaces betAveen the grains or along lines of solution or of jointing, 

cleavage, bedding, or other structure planes or fissures. Among the 

various types of reservoirs the following are the most important 

water producers:

Types of underground reservoirs.

I. Original forms.

A. Original pores.

B. Lamination planes.

0. Bedding planes.

D.'Vesicles (in igneous rocks only).

II. Secondary forms.

 A. Secondary pores.

1. Pores resulting from leaching and solution.

2. Pores resulting from recrystallization. 

B. Solution openings.

1. Isolated cavities.

2. Tubular channels.

3. Sheet openings. 

C. Mechanically eroded reservoirs.

1. Tubular channels.

2. Pocket openings.

3. Sheet openings. 

D. Fracture openings.

1. Irregular openings.

a. Desiccation cracks.

b. Contraction fissures. '

0 Fuller, M. L., Significance of the term "artesian :" Water-Sup, and I IT. Paper No. 160, 

U. S. Geol. Survey, 1906, pp. 9-15.
UNDERGROUND CONDITIONS. 9

. 

II. Secondary forms Continued.

D. Fracture openings Continued.

1. Irregular openings Continued, 

c. Torsion fractures, 

d. Shearing breaks, 

e. Vibration fractures, 

f. Explosion ruptures.

2. Joints.

a. Vertical joints. 

b. Horizontal joints, 

c. Parallel joints, 

d. Intersecting joints, 

e. Joint breccias.

3. Faults.

a. Single fault planes, 

b. Parallel fault planes, 

c. Irregular faults, 

d. Intersecting faults, 

e. Fault breccias.

4. Vein contacts.

5. Igneous contacts.

G. Shearing planes. 

E. Cleavage planes. 

F. Foliation and schistosity planes.

Most of the forms enumerated are not limited to any particular 

class of rock, but may be found in the stratified, metamorphic, and 

igneous types. The vesicles of igneous rocks, however, have no exact 

counterpart in stratified rocks, although the pores containing included water of sedimentation approach them in nature. Solution 

channels'are likewise usually, although not necessarily, found only 

in sedimentary rocks; foliation and schistosity are mainly features of 

igneous or metamorphic rocks, while lamination, as the term is here 

used, is a feature of stratified rocks.

ORIGINAL FORMS.

Original pores. The original pores include both the pores of the 

primary rocks and the unfilled spaces between the fragments or grains 

of the fragmental and other secondary rocks, including till, sand, and 

gravel; sandstone and conglomerate; oolite, shell .limestones, chalk, 

etc. The minute pores in clays, as well as the intercrystal spaces resulting from the contraction and adjustment incident to the cooling 

of igneous rocks, belong in this class, although- these are usually far 

less important than the macroscopic pores of the coarser sedimentary 

rocks. The original pores rank first in water-bearing capacity, characterizing all of the best-known types of water beds.

Lamination planes. Lamination planes, or the crowded partings 

which separate certain of the finer stratified rocks into numberless 

thin sheets or laminae parallel to the bedding, are of considerable im-
10 CONTROLLING FACTORS OF ARTESIAN FLOWS.

portance. Many shales, especially where the, partings have been 

somewhat opened by the weather near the surface, carry largo 

amounts of water in such planes. The general exudation of water 

from laminated beds, such as often occurs throughout a considerable 

vertical range where the layers are exposed in cliffs or in the artificial 

faces of quarries, is familiar to everyone.

. Bedding planes. Bedding planes, or the partings between individual layers or beds of the same or different classes of rock, often 

carry large amounts of water. This is in part due to the fact that the 

adhesion along such planes is less than that in a mass of homogeneous 

material, a condition which results largely from the imperfect contact due to variations of material, changes in texture, variations in 

arrangement, etc., which have resulted from changes or halts in deposition. This lack of adhesion makes the bedding planes more readily 

available for the passage of water than the body of the rock. Difference in permeability of the overlying and underlying layers is also 

a leading factor in the concentration of water along the bedding 

planes, making the latter, next to the original pores, the most important water containers. This is especially true where the planes have 

been somewhat widened by subsequent solution admitting the free 

passage of water, as shown in PL I, A.

Vesicles. Vesicles, or cavities resulting from the expansion of 

steam in cooling lavas, form a distinct although not a common type 

of reservoir. Usually the vesicles are very imperfectly connected, but 

in some of the Newark lavas, such as have been described by B. K. 

Emerson and others, the vesicular portions of the trap seem to form 

a definite water horizon. The same is doubtless true of many other 

scoriaceous lavas, both those occurring on the surface and those 

buried beneath subsequent deposits. The possibility of a general water 

movement through such materials is shown by their secondary mineralization, seen in both mines and surface exposures. The almost 

universal mineralization of the upper vesicular portions of the copper-bearing traps the amgydaloids of Keeweenaw Point, Lake 

Superior, is a particularly good illustration of deep-seated movements 

in such zones.

In the same class with the vesicles, though o£ different origin, may 

be placed the cavities due to contraction of igneous magmas on cooling, especially magmas of the acid type. Original, crystal-lined 

openings up to 3 feet in diameter have been noted by the writer in 

the pegmatites of New Hampshire, and minute cavities exist in many 

other rocks. While rarely important as containers of water, they are, 

nevertheless, of sufficiently common occurrence to necessitate their 

inclusion with the other possible reservoirs.
BULLETIN NO. 319 PL. I

'

A. THE BEDDING PLANE; SPRING EMERGING FROM BEDDING PLANE IN LIMESTONE.

H. RAMIFYING CHANNELS ALONG BEDDING PLANE IN LIMESTONE. 

ARTESIAN RESERVOIRS.
UNDERGROUND CONDITIONS. - 11

> ' SECONDAKY FOKMS.

> 

Secondary pores. By secondary pores are meant those, minute

"f spaces too small to be designated as openings or cavities which 

have resulted from the processes of weathering, solution, recrystalf -, lization, etc. Many of these are of much importance. The dolomitized portion of the Trenton limestone in parts of Ohio and Indiana, 

for instance, is sufficiently porous to carry considerable volumes of 

water; the original cement has been removed from calcareous sandstones in many areas, leaving them open and porous; soluble minerals, such as pyrite and calcite, are here and there leached from their 

relatively insoluble matrix, leaving notable open spaces; and the 

grains of crystalline, rocks become so loosened by weathering for a 

depth of many feet that the material absorbs water almost like a 

sponge. It is doubtless through the formation of secondary pores 

that circulation is established along many of the lamination and bedding planes, leading eventually to the formation of open solution 

passages.

Solution openings. These are among the most important of the 

secondary reservoirs and, as their name implies, are formed by the 

solvent action of percolating waters. They may be divided for convenience into (1) isolated irregular or roughly spherical reservoirs 

and (2) elongated passages or channels of tubular or sheet form.

The first of these types, at least where not connected with other 

. passages, seems to be of rare occurrence. Many geodes, however, 

showing horizontally banded fillings, occur in the body of limestones 

without connection with recognizable openings through which the 

mineralized solutions could have entered, the spaces apparently being 

first dissolved and then gradually filled by water entering through

' the pores of the body of the rock. It is not impossible that some of

the ore pockets in certain limestones may be of this origin, although

by far the greater part of these seem to be direct replacements.

. , Of the elongated passages or channels, the ordinary caves are the,

best examples (PL II, B). Some of them -are of great length, a

r ' single passage in the Mammoth Cave of Kentucky being over 8 miles 

long. Many such passages are 20 feet high; a few are as high as 75 

feet; and some are as much as 50 to 150 feet \vide. Some of the 

chambers which have been penetrated by mining shafts have shown 

hardly a trace of the openings through which the water entered or 

passed out, the openings simulating on a large scale the geode cavities described. The great vertical wells of the Mammoth and other 

caves, having diameters of 10 feet or more and depths of more than 

200 feet, and the similar '" natural wells " of Florida and elsewhere 

also belong to this class.
12 .CONTROLLING FACTORS OF ARTESIAN" FLOWS.

Many of the channels of this type have resulted from the enlarge- ' 

ment of joints, the action being-especially marked near the intersection of two or more planes, the great irregularity of some of the 

openings being accounted for by the complexity of the joint or 

fracture systems. This appears to be the case in the Joplin zinc 

district. Elsewhere, however, many of the largest passages follow 

bedding planes without reference to jointing, apparently having developed from one of the many meandering and branching passages 

that characterize such planes at many points. A view showing a network of small channels on one of these bedding planes is reproduced 

as PL I, B. The small channels are gradually enlarged and tend to 

coalesce and form a single large channel which, by continued solution, 

is gradually widened until a cave results. A few small tubular channels that pass diagonally through the rock without apparent connection with joints or bedding planes have been noted. The determining 

causes of such passages are not known, but it seems certain they 

represent simply the enlargements of some preexisting line of easy 

water movement.

The sheet form of solution passage is the first stage in the enlargement of joints, faults, or other planes. The secondary pores first 

formed eventually unite into an exceedingly narrow sheet-like opening. In crystalline and other insoluble rocks these may persist 

indefinitely, but in limestones differential solution soon develops the 

characteristic irregular cavities.

Mechanically formed reservoirs. These include (1) irregular, but 

usually more or less tubular, .passages, many of which are followed 

by waters, in clay, till, and similar materials, and (2.) certain of 

the water-bearing gravel pockets. The former may frequently be 

examined in detail where springs emerge from bluffs. In general 

they are from 1 to 4 inches in diameter, although larger ones doubtless occur, and are probably of considerable length. Their manner 

of formation is very similar to that of the limestone passages, except 

that the action is mechanical instead of chemical. The water finds 

its way along some bedding, joint, or other plane, gradually picking 

up and carrying away, particle by particle, the'fine material with 

which it comes in contact until an open passage finally results.

Allied to these passages in manner of formation are the gravel 

pockets in till. Flowing wells from tills have been known to bring 

up cartload after cartload of clay and fine sand, until the original 

mixture of clay and pebbles about the well has given place to a loose 

and open gravel. Similar pockets appear to have been formed in 

many places by natural circulation, where springs have broken 

through till 'deposits, and extensive layers of gravel are believed to 

have been produced \vhere general movements have occurred along 

lamination partings within the till.
U. s. GEOLOGICAL SURVEY

A. EARTHQUAKE CRACK FILLED WITH SAND DIKE, 

BETWEEN WALLS OF CLAY. IS. UNDERGRO

ARTESIAN RESERVOIRS.
U. S. GEOLOGICAL SURVEY

ARTESIAN RESERVOIRS; TORSION CRACKS DUE TO FOLD
UNDBBGKOUND CONDITIONS. 13

Fracture openings. Under this head are included a number of 

openings of varying character, due to a wide range of causes. Joints 

and irregular fissures are the most common types and may be classed 

according to the presence or absence of movement of the walls as 

simple or fault openings.

The immediate cause of all such openings is probably local tension, 

although, compression is frequently the indirect cause. Fractures 

resulting from the contraction of the rocks accompanying cooling, 

dehydration, etc., are caused solely by tension, but in expansion or 

dilation due to hydration, etc., the local tension giving rise to the 

fractures is simply an incidental result of the pressure resulting from 

the expansion. Similarly, the so-called compression fissures or cracks 

" formed in a rock cube subjected to heavy pressure, while resulting 

from the compression of the block as a whole, are in themselves due 

rather to local tension developed as a result of readjustments under 

the influence of the pressure. Again, in the case of rock folds, 

although pressure produces the arching, it is the tension developed 

by the bending that actually produces the fractures (PI. III). For 

convenience of discussion fracture openings are here divided into 

irregular openings, joints, faults, and' igneous and vein contacts.

Irregular openings. In this class are included several types of 

openings, such as the intersecting cracks formed by the dessication 

of wet silts, the fractures resulting from the contraction of igneous 

rocks on cooling, the breaks arising from the distortion of beds infolding, the gashes produced in the adjacent rock mass by the drag 

incident to faulting or by the movements accompanying expansion 

by hydration, the cracks caused by earthquake waves in soft materials (PI. II, A), and possibly certain profound fractures due to 

the general cooling of the earth's crust. In the same class should 

probably be placed the irregular but more or less circular openings 

connecting with surface " craterlets," formed by the occasional expulsion of gas 0 arising from the decay of woody matter in unconsolidated formations and by the expulsion of water through the body of 

the soil (not through the cracks) in time of earthquakes.6

Openings of the types outlined are of common occurrence and wide 

distribution, but in the main are of small size. Occasionally, IIOAVever, even where there has been no faulting, they are, as attested by 

fissure veins, of considerable width and have afforded passages for 

immense volumes of water.

Joints. For the purpose of this discussion the details of the origin 

of joints need not be considered, and they-may be simply defined as

0 Shuler, N. S., Conditions and effects of the expulsion of gases from the earth : Proc. 

Boston Soc. Nat. Hist., vol. 27, 1896, pp. 89-196.

6 Button, C. B.. The Charleston earthquake of August 31, 1886: Ninth Ann. Kept. U. S. 

Geol. Survey, 1889, pp. 203-328.
14 CONTKOLLING FACTOES OF ABTESIAN FLOWS.

smooth fracture planes cutting the rock in various directions, but unaccompanied by any differential movement of the walls. Joints vary 

in position from vertical to horizontal, but commonly make an angle 

of 70° or more with the horizon. The spacing also varies greatly according to the character of the rock and the disturbance to which it 

has been subjected, but on the whole the spaces between joints are 

greatest in sandstones and similar rocks and smallest in slates. In the 

latter rock it is not infrequent, to find, on the one hand, zones broken 

up by parallel joints into thin sheets (PL IV) and, on the other hand, 

zones cut up by intersecting joints into minute rhombs, converting the 

mass into what may be termed joint breccias (PL V, B). An investigation of the granites of Connecticut made by Mr. E. E. Ellis tt 

showed that the spacing of the vertical joints at the surface commonly ranged between 3 and 7 feet, while the horizontal joints varied 

from an average of 1 foot apart in the upper 20 feet of rock to 6 to 

30 feet apart in the succeeding 80 feet (PL V, ^L). The width of the 

openings varied from 2 inches at the surface to a fraction of a millimeter at depths of 25 to 100 feet.

Notwithstanding the narrowness of the joint openings, experience 

in mining regions and in quarries has shoAvn the existence of connecting systems extending over large areas. At Cripple Creek, for instance, as described by Lindgren and Ransome,6 the system of connecting joints extends over an area 3 miles in diameter and is so open 

that the entire tract might be drained from a single point. The volume of water held .in such a system is enormous and its removal by 

pumping often entails great expense to the mines. Quarries also 

frequently have trouble with water, and heavy pumps must sometimes be installed to remove it. . In general the circulation in vertical 

joints is much greater than in horizontal joints, water being especially 

abundant where two or more fractures of the former type intersect.

Vein contacts. Many of the contacts of veins with their wall rocks 

are characterized by extensive circulation of water, which, like the 

waters in joints, often interferes seriously with mining and adds 

greatly to its cost. In general, however, the passages are very small, 

the water following, at least at first, the almost inappreciable openings along the walls, where, as along many bedding planes, the Avater 

finds access because of the imperfect nature of the contact between unlike materials In true veins the original fracture is probably most 

commonly a joint plane, but deep irregular fissures are not uncommon. In segregation veins the contacts may be regarded as solution 

surfaces.

0 Ellis, E. E., Occurrence of water in crystalline rocks : Water-Sup, and I IT. Paper No. 

160, U. S. Geol. Survey, 1906, pp. 19-28.

1 Lindgren, Waldemar, and Ransome, P. L., Report of progress in the geological resurvey of the Cripple Creek district, Colorado : Bull. TJ. S. Geol. Survey No. 254, 1904, pp. 

31-32. ' 
U. S. GEOLOGICAL SURVEY 

.-i?^ A-"* v- 

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v ,-^A^ i- %>^^

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^<-^^^ \fARTESIAN RESERVOIRS: SHEET JOINTING.
U. S. GEOtOGICAL SURVEY IULUETIN NO. 319 PL. V

A. HORIZONTAL JOINTS IN GRANITE.

B. JOINT AND FAULT BRECCIA. 

ARTESIAN RESERVOIRS.
UNDERGROUND CONDITIONS. 15

Igneous contacts. What has been said of the vein contacts applies 

with equal force to the igneous contacts of the dikes or sills intruded 

into joints, bedding planes, or other preexisting fractures or lines 

of separation. In some places igneous masses, as certain acid pegmatites, have actually eaten their way into the country rock, and the 

contacts often have no relation to previous structures. They are, 

however, less likely to afford favorable conditions for the circulation 

of water than the contacts of the normal type.

Faults. Although faults are far less numerous than joints, they 

are more likely to be associated with extensive circulation systems 

than the latter (PL VI, ^1). This, in large measure, is the result 

of the movement of the Avails by which opposing projections are 

brought opposite one another, leaving intervening openings along 

which the water freely circulates. Sheeted zones, with large numbers of closely adjacent parallel fault planes, and crushed zones or 

fault breccias, are also common, arid likewise afford exceptionally 

good water passages and reservoirs (PI. VI, B).

Shearing planes. Shearing is closely allied to. faulting, inasmuch 

as it implies a differential movement of adjacent portions of the rock, 

but differs from faulting in that it usually comprises no lines of 

definite fracture, but consists rather of a readjustment of the material'along parallel planes throughout the rock. At the start there 

are no actual openings, but the shearing planes are lines of weakness 

and are more or less permeable to water, and, when near the surface, 

rapidly widen into material openings under the influence of the 

weather, often becoming reservoirs of importance.

Cleavage planes. These are more or less vertical planes, produced 

by the action of pressure, etc., on certain compact rocks such as slate. 

Unlike most joints, they are not ordinarily actual fracture planes, but 

are simply lines along which the rock tends to split under favorable 

conditions. It is not probable that they carry much water when at 

a depth, but near the surface, where they have been somewhat opened 

by the agencies of weathering, considerable quantities are frequently 

stored in them (PL VII, B).

Foliation and schistosity planes. These planes, dependent upon 

the parallel arrangement of the crystalline components of igneous 

or metamorphic rocks, are similar in many ways to the shearing and 

cleavage planes, being potential rather than actual rifts, but under the 

action of the weather appreciable openings holding considerable 

quantities of water soon develop'. Some weathered schists, appear 

to hold 15 per cent or more of their bulk of water (PL VII, A).

SOURCES OF UNDERGROUND WATER.

The probable source of underground waters has been widely discussed, and while everyone would doubtless agree that by far the
16 CONTROLLING FACTOES OF ARTESIAN FLOWS.

greater part is derived from rainfall there is a considerable variation 

of opinion as to the relative importance of the other sources, especially as to the part played by the sea and aqueous magmatic emanations. The common sources of underground waters are given below:

Sources of underground waters.

I. Atmosphere.

1. Direct.

a. Precipitation, 

b. Condensation.

2. Indirect.

a. Lakes, 

b. Streams.

II. Hydrosphere, or ocean.

1. Contemporaneously absorbed waters.

2. Originally included sea water.

III. Lithosphere, or crust.0

1. Primary waters.

a. Chemically excluded waters.

2. Secondary waters."

a. Physically excluded waters. 

TV. Centrosphere, or interior.0

1. Waters directly exclude:!.

2. Indirectly excluded magmatic waters.

WATERS FROM THE ATMOSPHERE.

Precipitation and condensation. Water from the atmosphere, aside 

from the amount entering immediately into chemical combination 

with surface materials, reaches the surface rocks either by precipitation or condensation. The following outline illustrates the disposal 

of the waters.

Disposal of. precipitation.

I. Direct evaporation before absorption or run-off.

a. Evaporation of the water film from soil and rock surfaces, vegetation,

etc.

b. Evaporation from undrained pools. 

c. Evaporation from snow surfaces. 

' II. Absorption by vegetation, 

a. Living. '

b. Vegetable mold, etc.

III. Direct run-off (without previous absorption). 

 IV. Absorption by soils and rocks.

The relative importance of the several methods of disposal will 

vary greatly according to temperature, humidity, vegetation, character of soils, and other related factors. In humid regions and with 

soils of average porosity the absorption by rocks and soils is by far

" These terms are used as defined by J. W. Powell, Mon. Nat. Geog. Soc., vol. 1, No. 1, 

1895, p. 1. ' .
 . " "' . "-' - - 

U. S. GEOLOGICAL-8URV)£Y~ BULLETIN NO. 319 PL. VI

.-1. SOLUTION CHANNEL ON FAULT LINE.

7?. CRUSHED ZONE ON FAULT. 

ARTESIAN RESERVOIRS.

1
U. S. GEOLOGICAL SURVEY BULLETIN NO. 319 PL. VII

A. SCHISTOSITY PLANES.

Jl. CLEAVAGE PLANES. 

ARTESIAN RESERVOIRS.
UNDERGROUND CONDITIONS. 17

the most important, probably accounting for at least 85 per cent of 

the precipitation. In certain sandy regions, as on Cape Cod, Long 

Island, it is probable that nearly or quite 95 per cent of the water 

enters the soil immediately, there being practically no direct run-off 

except on the rare occasions when rain fall son frozen ground or snow. 

In clayey regions and in areas of rock, especially where vegetation is 

very scarce, a large local and temporary run-off may result.

Any surplus of the water of condensation over that required to wet 

the surface of the ground and vegetation is taken up directly by the 

soil, there being practically no evaporation" under the existing conditions. Ordinarily the amount so derived is small, but it may become 

of some consequence in certain mountainous regions, where direct condensation is sometimes sufficient to form little rivulets of water on 

the condensing surfaces.

Waters from lakes and streams. One of the most common popular 

conceptions is that ground Avaters are derived either from neighboring 

or more remote lakes and streams. It is too well known to require 

more than the simple statement, however, that the movement of such 

water is normally toward and not away from the water bodies, the 

surfaces of which are below and not above the water table. It is only 

when there is some sudden rise of water in the lake or stream due to 

causes independent of local rainfall that the level becomes higher than 

the adjacent water table and~a landward, movement takes place. These 

conditions are illustrated by fig. 1. Such movements occur tempoFlG. 1. Section illustrating conditions governing movement o£ water away from streams 

or lakes. N, Normal position of water table; F, position of water table during floods.

rarily during the flood period of rivers fed from mountain snows, etc., 

or in lakes supplied by such streams. Similar conditions exist where 

the torrents resulting from cloudbursts temporarily flood certain parts 

of our great deserts.

WATEKS FKOM THE OCEAN.

Contemporaneous absorption. As in the case of rivers and. lakes, 

the ground-water movement is ordinarily toward the sea, but occasionally, especially in estuaries, severe storms bank up the waters to 

a height of several feet above their normal level for a considerable 

length of time. At such times movements of salt Avater into the sand 

may occur, sometimes seriously affecting adjacent sb.all.Qw wells,

3698 Bull. 319 OS -2
18 CONTROLLING FACTORS OF ARTESIAN FLOWS.

Other than under the above conditions, ocean water does not commonly penetrate inland. When the natural conditions are disturbed 

however, as when wells near the shore are heavily pumped, the water 

table may be sufficiently lowered to establish a reversed movement. 

Salt water also occasionally penetrates far inland where open solution 

channels in limestones now abandoned by the streams which formed 

them afford passages for it. Probably the most remarkable case of 

penetration by sea water is that at the so-called Sea Mills of Cephalonia in Greece, where a steady stream large enough to run a mill has 

from time immemorial left the sea and passed inland, finally disappearing into the porous limestone.®

The supposed causes of this phenomenon are discussed on page.30.

Originally included sea water. Sediments formed -in the ocean include large quantities of sea water, the amount varying from 10 to 40 

per cent or more of the bulk of the material according to its nature. 

Ordinary sands commonly hold about one-third,of their volume. If 

the marine beds are lifted above sea level while still in an unconsolidated condition much of this water will drain out except when 

the beds are so warped in the process as to form troughs or when 

drainage is prevented by the presence of overlying impervious beds.

The Cretaceous deposits near Wilmington, N". C., afford a good example of included waters in beds not yet uplifted, flowing wells of 

salt water being obtained at many points, even beneath impervious 

clays which effectually prevent any present access of the sea water. 

The pressure comes from the meteoric waters entering at the outcrop 

near the inner edge of the Coastal Plain, and as the salt water is removed fresh water takes its place. Instances of salt wells turning 

fresh have been described by the writer in another paper.6 Perhaps 

the best illustration of included water in older and uplifted rocks 

is that afforded by the salt waters of the thick, open sandstones of 

the Carboniferous series of western Pennsylvania, the waters occuring under conditions which seem to preclude their access to any saltbearing beds.

WATERS FROM THE ROCKS OF THE CRUST.

By waters from the lithosphere or crust are meant the originally 

combined or otherwise unavailable waters which have later been set 

free by physical or chemical exclusion. In their original form the 

waters are either primary (forming a part of the original minerals) 

or secondary (derived from absorption by some one of the methods 

outlined in the preceding sections).

" Crosby, F. W., and Crosby, W. 0., The Sea Mills of Cephalonia: Tech. Quart., vol. 9, 

1896, pp. 6-23. Fuller, M. L., Bull. Geol. Soc. America, vol. 18, pp. 221-232.

6 Fuller, M. L., Instances of improvement of water in wells: Water-Sup, and Irr. Paper 

No. 160, U. S. Geol. Survey, 1906, pp. 96-99.
TJNDEBGBQTJND CONDITIONS. 19

Chemically excluded waters: The chemically excluded waters are 

the originally combined waters which have been set free by chemical 

processes. As first formed numerous minerals are in the hydrated 

form, but later, usually through the influence of heat and pressure, 

lose the .whole or part of their water. This process of dehydration 

commonly takes place only at considerable depths, and usually results 

.from recrystallization or recombination due to metamorphism. In 

some cases the entire amount of water contained by the minerals is. 

excluded, but in others, as in some of the recombinations, only a part 

is driven out. Among the best illustrations of the processes are the 

exclusion of mechanically included waters by the crystallization of 

amorphous limestones as calcfte, by the change of certain gypsums 

through metamorphic action to anhydrite, and by the change of peat 

and lignite to coal. The action is not solely deep seated, there being 

more or less extensive dehydration, especially of iron compounds, in 

regions where hot and dry seasons alternate with periods of rainfall. 

Van Hise attributes the red hematitic stains, colorings, etc., of the 

deserts of southern California and" elsewhere to the dehydration of 

the iron from the limonite form.*

Since dehydration takes place mainly at considerable depths the 

water is not lost to the rock crust as a whole, but simply to the part 

undergoing alteration. Most 6f it passes upward into the more porous unaltered rocks, in which it may remain for an indefinite period.

Physically excluded ivaters. TliQ expulsion of secondary waters, 

including those derived from the process of dehydration in underlying rocks in the manner just described, as well as the included 

" waters of deposition," occurs mainly through the agency of pressure and heat. The exclusion by pressure is Avell illustrated by the 

violent expulsion of water along fault rifts during great earthquakes, 

an action which, although especially manifest at the surface, can 

hardly be confined to this zone, but must often occur between beds at 

considerable depths. The action of heat in expulsion will be most 

pronounced where water-bearing strata are penetrated by igneous intrusions, especially where ready escape for the steam or Avater into 

overlying beds is afforded by joint, fault, or other openings.

WATERS FROM THE CENTROSPHERE,

 The waters from the centrosphere may be divided into those reaching the reservoirs in the crust by direct emanation or exclusion, and 

those reaching the upper crust indirectly through igneous intrusions. 

As was shown by Hoskins,6 rock pressure limits the occurrence of open

" Van Hise, C. R., Some principles controlling the deposition of ores :' Trans. Am. Inst. 

MIn. Eng., vol. 30, 1900, pp. 27-177.

6 Hoskins, L. M., Flow and fracture 'o? ..ucks as related to structure : Sixteenth Ann, 

Kept. U. S. Geol. Survey, pt. 1, 181,'t,, pp. 845-875.
20 CONTROLLING FACTORS OF ARTESIAN FLOWS.

cavities in ordinary rocks to depths under 10,350 meters, but rockinclosed, liquid-filled cavities can exist to an indefinite depth at 

which water and molten rock are miscible in all proportions. The 

volume of aqueous matter in the central magma is an unknown 

quantity, but it is acknowledged that practically all lavas contain 

material amounts of water, and while some, if not most of it, may 

be derived from the rocks through which the lavas have passed, a 

part is doubtless derived from the original magma. It is not improbable that as the cooling of the central magma progresses considerable 

amounts of water are given off into the overlying rocks. This and 

the more common form of magmatic waters that given off from igneous intrusions together form, in the belief of many geologists interested in economic deposits, an important source of ore-depositing 

solutions. At any rate it may safely be said that it is often of great 

local importance.

CONFINING AGENTS.

In this discussion the confining agents in artesian systems are 

divided for convenience into bedded and jointed rocks. In the usual 

discussion impervious beds are ordinarily the only agents recognized, 

but observations made by a considerable body of field workers during 

the last four years has brought to light some new conditions of flow 

and has emphasized the importance of a number of factors that are 

seldom mentioned. The principal confining agents are as follows: -

Confining ayents. 

I. Bedded rocks.

A. Upper confining agents. ;

1. Impervious beds. .

2. Stratification. 

8. Friction.

4. Mineral crusts.

5. Frost zones.

6. Confined air and gas.

7. Fresh water.

8. Salt water. 

B. Lower confining agents.

1. Impervious beds.

2. Stratification.

8. Friction. .

4. Mineral crusts.

5. Frost zones.

6. Confined air and gas.

7. Fresh water.

8. Salt water.

9. Cementation.

10. Heat.

11. Pressure.
/ UNDERGROUND CONDITIONS. 21

II. Jointed and fractured rocks. 

A. Upper confining agents.

1. Impervious hanging wall.

2. Impervious surface coverings.

3. Frost fillings.

4. Vein fillings.

5. Weathering products.

6. Converging walls.

7. Interrupted joints.

8. Sea water. 

B. Lower confining agents.

1. Impervious foot walls.

2. Vein .fillings (cementation).

3. Converging walls.

4. Interrupted joints.

5. Fresh water. ;

6. Sea water.

7. Heat.

8. Pressure.

BEDDED ROCKS. 

UPPER COFFINING AGENTS.

Impervious bed. The term " impervious bed " is here used to designate a bed of stratified material through which water penetrates 

with difficulty the sense in which it has been used in practically all 

preAdous discussions of artesian waters. In general it has been assumed that such a bed relatively impervious as compared to the 

water bed is essential to artesian floAvs, and it has been so shown-in 

practically all figures illustrating artesian systems. As a matter of 

fact, hoAvever, it need not be absolutely impervious. In the words 

of Chamberlin,*1 " a stratum that successfully restrains the most of 

the water, and thus aids in yielding a floAv, is serviceably impervious." Clays furnish the best confining strata, being both impervious 

in character and free from open joints or other fractures that permit 

the water to pass through. Shales are. generally accounted as second 

in value. Some limestones, as the Clinton of southwestern Ohio, are 

good confining agents, but most rocks of this kind are broken by 

joints that afford numerous points of leakage.

Stratification planes. At several places, in Michigan and elsewhere 

floAvs have been procured from homogeneous sands; As has been explained in another report'? the cause of the confinement may probably 

be -found in the arrangement and shape of grains. All materials 

that afford flows of the nature described are stratified in other 

words, they were deposited in layers, which, though composed of

" Chamberlin, T. C., The requisite and qualifying conditions of artesian wells: Fifth 

Ann. Kept. U. S. Geol. Survey, 1885, p. 138.

6 Fuller, M. L., Two unusual types of artesian flow : Water-Sup, and I IT. Paper No. 140, 

U. S. Geol. Survey, 1905, pp. 41-45. '
22 CONTROLLING FACTORS OF ARTESIAN FLOWS.

material of uniform grain, were nevertheless laid down successively 

one over another as independent horizontal laminae. This process 

develops conditions that are more favorable to the transmission of 

water along the laminae than across them, due in part simply to the 

lamellar arrangements There is, however, another factor present 

namely, the irregularity of the shape of grains which has probably 

considerable influence in regulating the flow of water through the 

sand. In sediments, such as gravel and sand, the particles no matter 

how uniform their size are not symmetrical in shape. One axis is 

almost sure to be longer than the other (fig. 2), and when deposition 

takes place the grains have a strong tendency to arrange themselves 

with their longer axes horizontal and to overlap one another to a 

greater or less extent, like the shingles on a house, though, of course, 

far less perfectly (fig. 3). Under such conditions it is clear that,

FIG. 3. Arrangement of sand 

FIG. 2. Form of sand grains. grains in stratified deposits.

although the material is pervious and may hold large amounts of 

water, the passage of water across the planes of stratification will be 

difficult, at least as compared with its passage along those planes. 

A well that enters such material will afford an upAvard path for the 

water that is easy as compared with its passage through stratified 

material of the character described, and a flow will often result.

Friction. Friction alone seems to be competent under certain conditions to produce the necessary confinement, especially where the 

reservoir is fed at the bottom. If, for instance, water should enter at 

the bottom of a thick bed of fine, uniform, and structureless sand 

under a head sufficient to lift it 100 feet through the sand it would 

rise in a pipe tapping it at the bottom to a height greater than its 

level in the sand outside, the difference being determined by the relative amounts of friction in sand and pipe. This factor may be as 

common in producing flows as the factor of stratification described 

above.

0 This overlapping of grains has been described by W. O. Crosby in his discussions of 

" hard-packed " sand in glacial deposits at Clinton, Mass. (Tech. Quart., vol. 17, 1904, 

pp. 61-62 and 67-70.) Although such sand is so deposited or "packed" that it strongly 

resists the advance of the drill, it nevertheless absorbs large quantities of water.
UNDEBGBOUFD CONDITIONS. 23

Mineral crusts. When the water table is in porous materials and 

is fairly constant -in level, mineral matter is frequently deposited 

along the upper surface, forming a sort of crust. A number of such 

crusts have been noted in the drift deposits of Michigan, Minnesota, 

and other States, while they are very common indeed in many of the 

desert regions. In Minnesota the crusts are of both iron and lime, 

and some of them are several inches thick. The iron crusts have the 

appearance of bog ore, resembling the similar deposits in Michigan." 

As long as the water table remains stationary the crust has no effect, 

J}iit whenever a rise takes place, due to rainfall entering at higher 

points, the crust holds back the water with the result that a material 

artesian pressure is quickly developed. (See fig. 9, p. 41.) 

. In the desert regions the crusts, known- as " caliche," are composed 

mainly 

«y of calcium carbonate and occur at various levels, i ranging & O

from 3 or 4 feet below the surface to considerable depths. These 

crusts appear to be of different origin at different localities, being due 

in part to the evaporation of waters brought up by capillarity, as postulated by Blake; 6 in part to precipitation from underground waters, 

by reason of the loss of carbon dioxide on the release of pressure, as 

suggested by Lee; G and in part to downward leaching and concentration of rain Avaters, as urged by R. H. Forbes.(Z Like the crusts 

previously mentioned, they may serve as confining beds whenever 

there is any rise of the water table due to rainfall at higher 

points.

Frost zones. The action of frost zones, such as frozen soils, is very 

similar to that of the crusts just described. Such frozen crusts form 

at the bases of gentle slopes along valleys, or wherever the water table 

comes to the surface, and extend back under the high ground to points 

where the water is no longer within reach of frost. Where the slope 

is gentle this may be some distance. The soil farther back not being 

saturated is often not frozen at all, especially in sandy and other welldrained materials. Under such v conditions rain water not uncommonly sinks dowmvard in the unfrozen region and raises the water 

table, with the result that the pressure is transmitted beneath the frozen soil. If the frozen crust is penetrated at such times the water will 

flow.at the surface. (See fig. 9, p. 41.)

Confined air and gas. While waters rising under the influence of 

gas pressure are not regarded as artesian, air and gas can not be excluded from the list of confining agents. Water is just as effectually

" Leverett, Frank, Flowing wells and municipal water supplies in the southern portion 

of the Southern Peninsula of Michigan : Water-Sup, and Irr. Paper No. 182, U. S. Geol. 

Survey, 1900, pp. 8-9.

"Blake, W. P., Caliche of southern Arizona: Trims. Am. Inst. Min. Eng., vol. 31, .1.901, 

p. 220.

" Lee, W. T., Underground waters of Salt River valley, Arizona : Water-Sup, and Trr. 

Paper No. 130, TJ. S. Geol. Survey, 1905, pp. 107-111.

" Quoted by Lee, ibid., p. 110.
24 CONTROLLING FACTORS OF ARTESIAN FLOWS.

prevented from reaching the crest of a gas-bearing anticline by the. 

gas pressure as if an impervious bed intervened, and one is as truly a 

confining agent as the other. Confined air may likewise limit the rise 

of water in dome-like caverns in limestone, while confined air in earth, 

when prevented from upward escape by frozen or saturated soil zones, 

often acts temporarily as a confining stratum.

Fresh water. The action of fresh water as a confining agent can 

not be better described than in the words of Chamberlin : " 

Paradoxical as it may seem, water itself may form a confining agent. * * * 

If the water between the well and fountain head is actually higher than the 

latter, it will tend to penetrate the water-bearing stratum, so far as the overlying beds permit, and will, to that extent, increase the supply of water seeking 

passage through the porous bed, and will, by reaction, tend to elevate the 

fountain head, if the situation permit. I conceive that one of the most favorable conditions for securing a fountain is found when thick semiporous beds, 

constantly saturated with water to a greater height than the fountain head, lie 

upon the porous stratutn, and occupy the whole country between the well and its 

source. This is not only a good, but an advantageous, substitute for a strictly 

impervious confining bed. Under these hydrostatic conditions, limestone strata 

reposing on sandstone furnish an excellent combination.

It should be noted, however, that although an impervious cover is 

not postulated the water bed is assumed to be relatively more porous 

than the confining stratum, and no recognition is made of flows from 

uniform materials, as described on pages 21, 22. The latter, however, 

adds even more emphasis to the importance of water as a confining 

agent than did the conditions described by Chamberlin.

Sea water. When porous deposits extend outward beneath the 

sea, as along sandy coasts, the fresh waters moving from the land 

rise from below against the pressure of the sea water. As sea water 

has a specific gravity of approximately 1.027 it will hold up a column 

of fresh water of materially greater length, and when the head of 

the fresh water is less, as is frequently the case, than the excess of 

weight of the sea waters, the latter may act as effective confining 

agents. (See p. 43.)

LOWER CONFINING AGENTS.

What has been said of the upper confining agents applies in many 

instances with equal force to the lower confining agents. The under 

bed, like the upper, may be any " bed that successfully retains 

most of the water," whether absolutely impervious or not. Stratification planes may limit the downward.penetration of the water in 

thick beds as it does the upward movement, and friction may produce 

the same result, especially in slightly inclined beds of great extent. 

Mineral crusts are more common as an upper restraining agent than

" The requisite and qualifying conditions of -artesian wells : Fifth Ann. Kept. U. S. Geol. 

Survey, 1885, pp. 138, 140.
UNDERGROUND CONDITIONS. ' 25

as a lower, but cases undoubtedly occur where the water is confined 

between two such layers. Water is found between frozen layers of 

soil in Alaska. Confined air often acts temporarily as an under 

confining agent, as in the saturated zones upheld by the air of soils 

during heavy downfalls of rain, and confined gas may possibly act 

similarly. Previously absorbed fresh Avaters, by saturating the 

deeper rocks, limit the depth of circulation of waters entering subsequently. Sea water is even more important as an underlying stratum 

than as an upper confining layer. In addition to the precedingagents, which act both as upper and lower confining agents, general 

cementation, heat, and pressure are effective factors in- limiting the 

downward penetration of water under certain conditions. 

Cementation. Cementation is the process' by which the grains of

sedimentary rocks are bound together and the intervening pores filled 

by the deposition of mineral matter from infiltrating solutions. Unlike the formation of crusts, this deposition does not result from 

evaporation, but from the supersaturation of solutions at depths far 

.below the water table. It is not usually limited to a single layer, or 

point, but is a general process affecting large bodies of rock over wide 

areas. The conversion of open porous sandstones to dense impervious 

quartzites by the deposition of silica is perhaps the best example of 

the process, which is notably efficient in limiting the downward penetration of waters.

Heat. It has often been assumed that the circulation of water, 

owing to its supposed conversion into steam, is limited to relatiA'cly 

moderate depths, but it can be readily shown that the rise of the boiling point due to increased pressure ordinarily more than counterbalances the increased heat at great depths, and that under any of the 

usually accepted rates of increment, change to steam will not take 

place. When water approaches uncooled- igneous intrusions that lie 

at shallow depths, however, conversion to steam may occur, and the 

downward penetration of the water may be stopped. This is probably a common factor of limitation in igneous regions and may possibly act in regions where the temperature gradient is particularly high.

Pressure. Pressure-, as shown by Hoskins/1 closes all ordinary cavities at about 10,000 meters and imposes an effectual limit to the penetration of free water, although rock-inclosed, liquid-filled cavities 

can exist to a depth at which water and rocks are miscible in all proportions. As a matter of fact, pressure is probably rarely an important factor in limiting the penetration of water in the unaltered 

bedded rocks because of their essentially superficial occurrence.

0 Hoskins, L. M.. Flow and fracture of rocks as related to structure: Sixteenth *Ann. 

Kept. U. S. Geol. Survey, pt. 1, 1890, pp. 845-875.
26 -CONTROLLING FACTORS OF ARTESIAN FLOWS.

JOINTED ROCKS. 

UPPER CONFINING AGENTS.

InCpervious wall. In the same way that an impervious .overlying 

bed is a leading restraining agent in bedded rocks the impervious 

hanging wall of an inclined joint is a prominent confining agent in 

jointed rocks. Like the former, it may not be absolutely but only 

relatively impervious, but owing to the fact that joints are mainly 

developed in dense or massive rocks, especially in the fine-grained 

types, the joint wall is on the average considerably more impervious 

than the cap rock in bedded formations. -

Impervious covering on surface. This is a very common restraining agent in jointed or fissured rocks. It is especially well shown in 

the extensive " lake-bed " region of southeastern Michigan, where 

artesian water, under pressure enough to lift it to the surface, is confined over considerable areas in jointed and fissured limestone, etc., 

by the overlying clayey till and " lake-bed " deposits.* The numerous flows from granite beneath alluvium in valleys in the Piedmont 

area of the Southern States is due to the same causes. (See figs. 11 

and 14, pp. 41, 42.)

Frost fillings. In winter water freezes almost as fast as it seeps 

out at the surface, and it is not uncommon to find that joint openings 

through which water is-ordinarily rising are frozen solid to some 

distance from the surface. The ice under such conditions may 

present an effective barrier to the water pressing upward from below.

Vein fillings. Water coming up from -below and carrying an excess of mineral matter in solution not infrequently deposits it in the 

openings near the surface, sometimes closing the joint openings as 

completely as they are closed by ice. Mr. G. O. Smith has described 

such fillings and considers* them the probable confining agents that 

give rise to the artesian flows from the crystalline rocks in parts of 

New Hampshire and Maine. 2* Weathering products. The usual action of the weather is to widen 

the joints and other partings, but occasionally, where the circulation 

is slight, the clayey products of decomposition are not entirely removed, but collect in the joints and other available openings, sometimes clogging them sufficiently to render them -effective obstacles 

in the path of uprising waters. The closing of joint passages due 

to the expansion resulting from the process of hydration in rocks 

undergoing weathering is also a possible factor in restraining underground water circulation.

"fuller, M. L., Two unusual types of artesian flow : Water-Sup, and Irr. Paper No. 145, 

U. S. Geol. Survey, 1005, pp. 40-45. .

6 Water resources of the Portsmouth-York region, New Hampshire and Maine : WaterSup, and Irr. Paper No. 145, U. S. Geol. Survey, 1905, pp. 120-128.
NATURE OP ARTESIAN CIRCULATION. 27

Sea water. Because of. its greater density, sea water e^xerts in 

jointed rocks, as in bedded rocks, a decided restraining influence on 

uprising fresh waters, even when, their head is somewhat higher than 

sea level, and it is a possible factor in affording1 the confinement necessary for some of the flows from jointed rocks when near sea level.

Converging walls. The converging of the joint walls near the top 

may be due to mineral deposition on the sides, to expansion of the wall 

rock due to weathering, to local pressure developed through faulting 

or readjustments of the joint blocks, or to the relative absence of solution as compared to that at greater depths. A contraction of the 

opening sufficient to exert a decided restraining influence on the 

underground waters may result from any of the causes indicated.

Interruptions of joints. Joints are not of unlimited extent, although some of the master joints may be miles in length. A joint 

may terminate either by gradual contraction and disappearance or 

by ending abruptly against an intersecting joint or other plane. 

This is especially true of intersecting horizontal and vertical joints, 

the latter frequently ending abruptly against the former. As most 

horizontal joints &~^ less open than vertical joints, the termination 

is at many places s -> as to prevent circulation beyond it.

LOWER CONFINING AGENTS.

The lower confining agents are not greatly different from the similar agents in bedded rocks or from the upper confining agents in 

jointed and fractured rocks already described. The impervious foot 

wall is comparable with the impervious hanging wall and is subject 

to the same qualifying statements. Frost filling and weathering play 

little or no part in fixing the lower limit of penetration, but vein fillings are as likely to occur at considerable depths as at the surface, and 

are probably not infrequently a factor of importance. The convergence of walls and the interruption or termination of joints are doubtless of even greater importance than as upper confining agents. Fresh 

and sea waters limit the downward penetration as in the bedded rocks, 

and, similarly, heat and pressure may locally pla}^ important parts.

NATURE OF ARTESIAN CIRCULATION.

Artesian circulation takes place by virtue of the variations in the 

pressure to which the water is subjected in different parts of its 

reservoir. By definition of the artesian principle (p. 7) all factors 

except hydrostatic pressure are excluded as determining causes of 

circulation. There are, nevertheless, a number of modifying agencies 

which in some cases exert a powerful influence on the water head or 

movement. The more important of the controlling and modifying 

factors may be summarized as follows :
28 CONTROLLING FACTORS OF ARTESIAN PLOWS.

Factors in artesian circulation.

I. Primary factor. 

A. Gravity.

II. Modifying factors.

A. Factors mainly affecting pressure.

1. Barometric variations.

2. Temperature variations.

3. Density of waters.

a. Variations clue to temperature, 

b. Variations clue to dissolved salts, 

c. Variations clue to suspended solids.

4. Height of adjacent water levels, 

a. Water table. 

1). Neighboring water bodies, 

c. Levels dependent on floods, 

d. Levels dependent on tides, 

e. Levels dependent on winds.

5. Bock pressure. 

B. Factors mainly affecting movement.

1. Porosity.

2. Size of grain or openings.

3. Temperature.

PRIMARY FACTOR.

Gravity. The leading factor in artesian circulation is gravity, 

from which fact it follows that (disregarding friction) the pressures 

in the opposing arms of an artesian system will be proportional to 

the heights of the respective water columns, while the effective head 

will be determined by the difference in trie two. The hydrostatic 

pressure dependent on gravity is the sole recognized cause of artesian 

pressure as the term is here used (p. 7) , although its action is 

modified in many ways by the qualifying factors considered below.

The operation of the ordinary hydrostatic law is limited to appreciable openings. According to Daniel ° such openings, which are 

known as supercapillary and. include joints, faults, bedding planes, 

some fissility planes, the pores of sandstones, etc., have for their 

minimum limit a diameter of 0.508 mm. in tubular passages and a 

width of 0.254 mm. in sheet openings of th.e joint or bedding-plane 

types.

MODIFYING FACTORS.

The factors which modify the pressures resulting from gravity may 

be divided into those which cooperate directly with the latter in determining the hydrostatic pressure, and those which primarily affect 

the movement of the.water and only incidentally influence the pressure. 6

a Daniel, Alfred, Text Book of Physics, 3d ed., 1894, pp. 277, 316.

6 For an extended discussion of the factors giving rise to fluctuations of water level, see 

Veatch, A. C., Fluctuations of the water level in wells: Water-Sup, and Irr. Paper No. 

155, U. S. Geol. Survey, 1906.
NATURE OF ARTESIAN CIRCULATION. 29

FACTORS MAINLY AFFECTING PRESSURE. 

BAROMETRIC VARIATIONS.

For each locality there is a normal barometric pressure dependent 

upon elevation, latitude, and distance from the ocean. This, howL ever, is subject to many influences, both cyclic and irregular, which 

materially modify the ultimate pressure. The barometric factors

r may be classified as follows:

Barometric factors.

^ I. Constant factors. 

.;' 1. Elevation. 

\.. - 2. Latitude. 

.J . 3. Distance from ocean.

* ; II. Variable factors.

 M: 1. Cyclic.

a. Diurnal variations. 

- b. Seasonal variations;

c. Variations clue to solar movements.

d. Variations clue to lunar movements. 

2. Irregular.

a. Atmospheric disturbances. 

j. ' . b. Cyclones. 

' *' c. Storms. 

r; d. Cloudiness. 

I 8. Topographic surroundings (independent of altitude).

( Although many of the factors .are very weak in their action all are 

; measurable, and, with the exception of solar and lunar movements, 

£ cloudiness, and topography, all are known to exert an appreciable 

)' influence on wells. In some instances the resultant effects appear to 

I be far greater than those that would be due to the actual differences 

in pressure at the point of observation. The cause of this is as yet 

unknown, but it is possible that it may prove to be related to those 

] producing the remarkable seiches of the Great Lakes, some of which 

\ are marked by a change of water level as great as 6 feet. It is not improbable that under favorable conditions all the variations noted 

have a material effect on underground waters. The manifestations 

are most noticeable at periods of low barometer and include increase 

of head, increase of flow, muddiness, and discoloration.

TEMPERATURE VARIATIONS.

\ Temperature acts on artesian circulation through its influence on

 the viscosity of the water, through the expansion and contraction of

included air or gas, by variations in the pressure of confined air or

gas upon water surfaces, and by its influence on the density of the

artesian waters. Of these viscosity mainly affects the water move-.
30 CONTROLLING FACTORS .OF ARTESIAN FLOWS.

merit directly, although it incidentally affects the head through its 

influence on .friction. The expansion and contraction of included 

gases has a direct affect on pressure and head. The influence of temperature on density is considered beloAv.

DENSITY OF WATERS.

Variations clue to temperature. Water expands about 4.3 per cent 

when heated from its point of greatest density (39.2°) to the boiling 

point and gives rise, in the case of long columns, to notable variations 

of volume and density. The difference in weight of cold and Avarm 

columns, and the resultant increase in the length of the. latter, has 

been cited as an important factor in deep circulation, especially at the 

Sea Mills of Cephalonia." The considerable streams which leave the 

ocean at this point and disappear into limestone crevices at sea level 

can only regain the surface at equal or higher levels. This result can 

apparently be attained only through the action of temperature or 

some other force that affects the density.

Variations due to dissolved salts. Besides temperature, the weight 

of water depends largely upon composition, the weight increasing 

materially according to the amount of,mineral matter in solution. 

Sea water has a specific gravity of 1.027 as compared with 1, the 

specific gravity of fresh water, from whichdt follows that a column of 

salt water 100 feet in height will support nearly 103 feet of fresh 

water. Even allowing for only relatively slight variations in density 

we have sufficient differences in pressure to produce circulation. 

This is thought to be a more effective cause than temperature in producing the circulation at the Sea Mills of Cephalonia mentioned 

above. 6

Variations due to suspended solids. The action is similar to that 

61 dissolved mineral matter, but is usually much more pronounced. 

It is best illustrated by certain phenomena exhibited in the jet process 

of well drilling, in which clear water is forced under pressure down 

a small tube inside a larger one, the materials detached by the current 

being carried to the surface in the space between the inner pipe and 

the outside casing. When the pressure is removed from the small 

tube the water is often found to rise in it materially above the height 

of the well and to flow for some moments at elevations several feet 

above the surface, the water between the inner and outer tube sinking 

at the same time. . This peculiar action seems to be due entirely to 

the high density of the mud- or sand-laden waters in the large tube as 

compared with the clear and lighter water in the inner pipe.

« Crosby, F. W., and Crosby, W. 0., Tech. Quarterly, vol. 9, 1896, pp. 6-2?.. 

6 Fuller, M. L., Conditions of circulation at the Sea Mills of Cephalonia: Bull. Geol, 

Soc. America, vol. 18, pp. 221-232.
NATURE OF ARTESIAN CIRCULATION. 31 

HEIGHT OF ADJACENT WATER LEVELS.

Water table. The height of the water table over any point in an 

artesian system may exert a material influence on the pressure. In 

fact, this may be a far more important factor than the pressure transmitted from the more remote catchment area. This action has been 

discussed in greater detail on page 24.

The level of the water table is controlled by a great number of factors, among which may be mentioned the amount of rainfall, the 

amount of evaporation, and the porosity of materials. The ground 

water does not usually respond at once to the rainfall, owing to 

the length of time that the water requires to penetrate the unsaturated upper materials; nor does the rise correspond in amount to the 

precipitation, because of losses by evaporation, absorption by vegetation, and the retention of a portion in the mi saturated zone. In very 

heavy rainfall a saturated zone may be formed at the surface, constituting a temporary perched water table, when the main water table 

may be affected almost immediately owing to the transmission of 

pressure by the air confined beneath the saturated layer.

Neighboring water bodies, etc. The level of lakes and streams is 

commonly a function of the height of the ground water in the vicinity, but sometimes the reverse is true and the ground-water level becomes a function of the level of the water bodies on the surface. The 

latter may also in some cases influence to considerable extent the 

pressure on underlying confined watei-s.

The effects of surface water bodies on the underground waters may 

be summarized as follows:

Effects of height of surface water bodies on underground waters.

I. Changes of ground-water levels.

1. Changes due to variation of level of surface streams receiving groundwater discharge.

2. Changes due to movements away from surface water bodies.

II. Variations of pressure on confined waters.

1. Changes due t6 communication between surface and underground 

water bodies through intervening beds. 

. a. Communication through joints and other passages. 

b. Communication through the body of .the intervening beds.

2. Changes due to transmission of pressure through intervening beds. 

^, 3. Changes due to plastic deformation.

The cause of the changes of ground-water levels resulting from 

variations in the height of the surface water bodies which receive 

the underground drainage is apparent. When such bodies are low 

the movement of ground waters is accelerated and the water table 

depressed, while when they are high the underflow is slackened and 

the water table elevated.
32 'CONTROLLING FACTORS OF ARTESIAN FLOWS.

In pronounced rises of the water levels in surface bodies due to 

floods, tidal fluctuations, banking of waters under the action, of 

strong winds, or to other causes arising from conditions developing . 

outside of the immediate area affected, the ground water is no longer i 

able to issue at its normal level. In fact the rising'waters act 

primarily as a dam, raising the level of discharge of the ground 

waters and ponding them up like the backwater behind an artificial 

dam. When the rise is more rapid than in the inflowing ground 

water an actual outward movement from the surface body may take 

place, producing a corresponding rise of the ground water.

Another effect of the rise of surface waters is a downward penetration of such water (due to the increased pressure) through the 

underlying retaining beds into more porous water beds below. This 

takes place in part through joints and similar passages,. which are 

present even in soft, unconsolidated clays, and in part, perhaps, 

through the body of the material itself. In either case a very slight ^ 

movement is sufficient to produce a pronounced rise in the waters of 

wells. Considering an area 1,000 feet square, a doAvmvard water 

movement of only one one-thousandth of a millimeter through a clay 

or other capping would be equivalent to a rise of approximately 25 

feet in a single well, or 1 foot in 25 wells.

The transmission of pressure through the so-called impervious beds 

is probably sometimes, a factor of artesian head, even though no 

movement of water through the beds takes place. Some quicksands, r 

although they AN-ill yield little or no supplies to a Avell, often carry f 

from 30 to 50 per cent of Avater, some of Avhich is in supercapillary j 

openings and hence is capable of transmitting hydrostatic pressure 

even when motion is prevented by excessive friction (using the term 

in its broader sense to.include the resistance of inertia as well as the 

resistance to motion).

Still another result, Avhich may be more common than is usually 

suspected, is the increase of pressure on confined Avaters, due to the 

plastic deformation of impervious beds under the varying loads 

resulting from changes in the water level of OA^erlying streams, lakes, 

or the sea. This is especially noticeable in Avells along the sea coast, 

Avhich commonly fluctuate with the tide, even though the water horizon lies deep beloAV the surface and is separated from it by thick ' 

beds of impervious clays, etc. The figures applying to the downward 

water movement in the preceding paragraph are equally applicable 

to deformation and emphasize the slight amounts necessary to account for the observed fluctuations in wells. .
EEQUISITES OF AETESIAN FLOWS. 33 

ROCK PRESSURE.

In addition to the deformation of the nature described in the preceding paragraph, pressure may be exerted by virtue of the. weight 

of the overlying materials alone. .This is probably not a common. 

factor, but extensive sinkings of the ground have followed the pumping of water from mines and the withdrawal of the support afforded 

by hydrostatic pressure, indicating that the rock pressure on the 

water must have been considerable, at least locally.

In the process of warping and folding the pressure of the rocks 

on the waters in their joints or other openings may often be important, especially when the disturbance is accompanied by faulting. 

Considerable .quantities are excluded from such openings during 

earthquakes, and it is probable that the action underground is of 

much greater extent than the surface manifestations.

FACTORS MAINLY AFFECTING WATER MOVEMENTS.

The principal factors affecting. underground water movements are 

porosity, size of grain or openings, and temperature. The first and 

second are factors of capacity, while all three are factors of friction. 

Their action is not wholly on movement, but through friction they 

have a decided, though indirect, influence on pressure. From the 

formula of velocity as computed by Alien Hazen a the following expression for loss of head is obtained : h= 72

In this formula h is the loss of head, v the velocity in meters daily, 

I the distance through which the water passes, c a constant factor, approximately 1,000, d the effective size of grain in millimeters, and t the 

temperature on the centigrade scale. For velocity the formula 

becomes:

From these formulae it appears that high porosities, large grains, 

and high temperatures all accelerate water movement.6

REQUISITES OF ARTESIAN FLOWS.

Having outlined the more important conditions bearing on the 

occurrence and movements of underground waters, we are in a position to discuss the controlling factors of artesian flow. In doing 

this it is necessary to point out some of the objections to certain of 

the commonly postulated requisites.

0 Some physical properties of sands and gravel : Kept. Massachusetts State Board of 

Health, 1892, p. 541.

" For a detailed description of the action see paper by C. S. Slichter on The motion of 

underground waters : Water-Sup, and Irr. Paper No. 67, U. S. Geol. Survey.

3698 Bull. 319 08 3
34 CONTROLLING FACTORS OF ARTESIAN FLOWS. 

OBJECTIONS TO COMMON REQUISITES. .

Since the appearance in 1885 of the paper of T. C. Chamberlin on 

the " Requisite and qualifying conditions of artesian wells " a a single 

set of requisites has, with one or two exceptions, been followed by 

writers of underground water papers. These, in brief, are as follows: 

(1) A pervious stratum to permit the entrance and the passage of 

water; (2) a water-tight.bed below to prevent the escape of waterdownward; (3) a like impervious bed above to prevent the escape 

upward, for the water, being under pressure from the fountain head, 

would otherwise find relief in that direction; (4) an inclination of 

these beds, so that the edge at which the waters enter will be higher 

.than the surface at the well; (5) a suitable exposure of the edge of 

the porous stratum, so that it may take in a sufficient supply of water; 

(6) an adequate rainfall to furnish this supply; and (7) an absence 

of- any escape for the water at a level lower than the surface at the 

well.

There is one very serious objection to the requisites outlined above, 

namely, they apply only to a single class of flows those from stratified rocks and neglect not only flows from other varieties of rock, 

but even other types of flow from the same rocks. There are, moreover, many exceptions to the postulated requisites, which, taken in 

connection with the limitations mentioned, make new and more comprehensive definitions desirable. Some of the objections to the requisites are mentioned below. . Pervious stratum. A pervious stratum, although a common form 

of reservoir, is seldom essential to artesian flows. In addition to 

the porous stratum postulated by the first requisite, flows may be obtained from lamination, bedding, cleavage, and shearing planes, from 

solution passages and mechanically eroded reservoirs, from vesicular 

zones in igneous rocks, from irregular joint and fault fractures, and 

from vein and igneous contacts. Metamorphic and igneous, as well 

as stratified rocks not only may, but actually do, yield flows at a large 

number of places; at many others the water falls only a few feet 

short of the surface; while in practically all wells the waters rise 

materially when encountered that is, are truly artesian.

With the exception of the vesicular lavas the sources of water 

mentioned are not in the nature of beds, but are in the form of actual 

openings, a type of passage not recognized in the older requisites.

Impervious bed below. In view of the nature of the reservoirs 

mentioned in the preceding paragraph and discussed in greater detail 

on pages 8-15 .it is apparent that the second requisite the impervious underlying stratum loses much of its force. Such impervious

« Fifth Ann. Rep. U. S. Geol. Survey, pp. 125-173.
REQUISITES OF ARTESIAN FLOWS. 35

beds are, it is true, adjuncts to many flows in stratified rocks, but 

numerous other agents may serve the same purpose. In bedded rocks 

the following may be mentioned: Stratification, friction, mineral 

crusts, frost zones, confined air and gas, fresh or salt water, cementation, heat and pressure. In jointed and fractured rocks impervious 

foot Avails, vein fillings, converging walls, interrupted joints, fresh 

and salt water, heat and pressure are the most important. Discussions of the agents in bedded rocks will be. found on pages 24-25 and 

of jointed and fractured rocks on page 27.

Impervious bed above. The objections to the postulation of an 

upper impervious bed are similar to those of the lower confining 

bed just enumerated. In the bedded rocks the following, in addition 

to the postulated impervious stratum, may serve as confining agents: 

Stratification, friction, mineral crusts, frost zones, confined air and 

gas, fresh water, and sea water. In the jointed and fractured rocks 

the impervious hanging wall, impervious surface coverings, frost and 

vein fillings, weathering products, converging walls, interrupted 

joints, and sea water may be mentioned in addition. For. a discussion 

of these agents see pages 21-24, 26-27.

fnclination of beds. Inclination of the water-bearing bed, while 

a common factor of artesian flows, is by no means essential. At many 

places water appears to penetrate lenses of sandstone in rocks, like 

those of the Carboniferous of Pennsylvania, through joints and similar openings, and flows may be obtained independent of any inclination of the bed affording the water. The same.is true of the horizontal beds yielding flows by virtue of the opposition of the stratification 

planes to upward movements, as described on page 22. Joint and 

solution passages also afford artesian.flows independent of any inclination at the point penetrated.

In both bedded and crystalline rocks the pressure must of course 

be transmitted from connecting passages or other water reservoirs at 

higher levels, but the supply itself does not necessarily come from a 

higher level, since besides the downward moving meteoric waters, 

sea waters, waters chemically or physically excluded from the crust, 

and waters excluded directly from the centrosphere or indirectly 

through magmatic intrusions all furnish supplies. These sources are 

discussed on pages 17-20.

Outcrop of porous stratum. The postulated suitable exposure of 

the edge of the porous stratum so that it may take in a sufficient supply of water, though a common, is likewise far from an essential 

factor of artesian flows. The horizontal sandy beds from which the 

flows are obtained in Long Island and Michigan, as described on 

page 22, nowhere outcrop, the water.penetrating directly downward 

through the overlying layers. It is believed that in many other 

places the water and pressure are communicated to the deep-lying por-
36 , CONTROLLING FACTORS OF ARTESIAN FLOWS.

cms beds through joints rather than from remote outcrops. Moreover, throughout extensive areas of the Silurian, Devonian, and Carboniferous rocks in Pennsylvania, West Virginia, and Ohio, in the 

areas underlain by Cretaceous beds near Fort Monroe, Va., in the 

region about Wilmington, N. C., and in many lesser areas elsewhere, 

the deep artesian waters appear to represent originally included sea 

waters and not waters entering at the outcrops. Other sources, including waters derived from the crust by chemical or physical exclusion or by direct or magmatic exclusion from the centrosphere, may 

furnish artesian supplies independent of the conditions of outcrop. 

(See pp. 17-20.)

Adequate rainfall. Since the salt waters of the Carboniferous and 

Coastal Plain rocks just described, as well as magmatic waters, are 

actually derived over extensive areas from sources other than rainfall, 

it is clear that rainfall should not be regarded as an absolute requisite 

to artesian flow.

Points of escape. There are very few artesian systems in which 

there is not more or less leakage. In the thicker and more persistent 

beds the leakage is often sufficient to insure circulation for long distances from the outcrop. Thus, in the Cretaceous beds beneath 

Charleston, S. C., and Savannah, Ga., fresh water has replaced salt 

water at least as far as the sea'coast, or over a distance of more than 

100 miles from their outcrop. At Fort Monroe, Va., and at Wilmington, N. C., on the other hand, there, appears to be but'little leakage, 

and the fresh water circulation is much less extensive, only salt water 

being obtained at the localities mentioned. The absence of leakage 

appears to have determined the presence of salt waters in the oilbearing rocks of Pennsylvania and. else where.

In order that leakage may prevent flows, it must take place near the 

point at which the water horizon is tapped. Chamberlin and others 

have shown that its influence is limited, and the requisites should 

therefore postulate the absence of near-by leakage rather than the 

entire nonoccurrence of leakage.

ESSENTIALS OF ARTESIAN FLOWS.

The essentials of artesian flows, as recognized by the writer, are as 

follows:

1. An adequate source of water supply.

2. A retaining agent offering more resistance to the passage of 

water than the well or other opening.

3. An adequate source of pressure.

The first requisite is not made specific as regards source, because, 

as has been pointed out, artesian waters are not derived from a single 

but from a variety of sources. The second requisite the retaining
KEQUISITES OF ARTESIAN FLOWS. 37

agent may be a stratum, a vein or dike wall, a joint, fault, or other 

fracture plane, a water layer, or some one of a variety of other agents. 

(See pp. 20-27.) The pressure, although primarily due to variations in level in the different parts of the artesian system, may be 

transmitted in so many ways and is subject to so many modifying 

factors that the postulation of a specific cause is impracticable.

MODIFYING FACTORS.

It is believed that the three factors stated in the preceding paragraph are all that can be considered as essential to artesian flows, all 

other postulated requisites being in' reality modifying or accessory 

rather than essential factors. These secondary factors may be classified as follows:

Secondary factors of artesian flows.

I. Hydrostatic factors.(renting to pressure and movement).

1. Factors mainly affecting pressure, 

a. Barometric pressure, 

b. Temperature, 

c. Density, 

d. Rock pressure.

2. Factors mainly affecting movement, 

a. Porosity.

b. Size of pores or openings, 

c. Temperature.

II. Geologic factors (relating to reservoir).

1. Character of reservoir.

2. Retaining agents.

3. Structure of reservoir.

4. Topographic conditions.

5. Conditions relating to supply, 

a. Catchment conditions, 

b. Condition of underground feed.

6. Conditions of leakage.

The action of the various factors has already been indicated in connection with the foregoing discussion and no further statements are 

necessary. , 

TYPICAL ARTESIAN SYSTEMS.

In closing attention may be called to a number of the more common types of artesian systems. The artesian basin is the one most 

commonly figured, but in reality it is far less common than the 

artesian slope. Artesian flows from uniform horizontal beds appear 

to be common in many places, especially in the drift deposits of 

Michigan, but the areas of such flows in a single locality are limited. 

Flows from bedding planes appear to be not infrequent in the denser 

rocks, in which the beds themselves are not porous, but they depend 

on local conditions, and the flows can seldom be predicted. Flows
38 CONTROLLING FACTORS OF ARTESIAN FLOWS.

from solution passages appear to be fairly common, notwithstanding 

the local character of the passages. The necessary confinement 

doubtless results from constrictions of the openings due to local zones 

of relatively insoluble rock,'to clogging by debris entering through 

sinks, to the caving of the walls, to the accumulations of silt iir*the 

more sluggish passages, etc. Flows from lamination planes appear 

to occur in certain shales and slates, while joints furnish one of the 

most widely prevalent types of artesian systems in the country. In 

fact practically all crystalline rocks, both igneous and metamorphic, 

as well as the jointed types of sedimentary rocks, contain water under 

strong artesian pressure; and while flows are not abundant they are 

found at short intervals throughout the Piedmont Plateau of the eastern United States and will doubtless eventually be discovered at many 

other points where such rocks occur at'the surface.

The following diagrams will- serve better than descriptions to indicate the nature of some of the more common artesian systems.

ARTESIAN BASIN.

The section shown in fig. 4 presents a set of conditions that occur 

in typical form in the Dakota sandstone basin.

FIG. 4. Section of an artesian basin. A, Porous stratum; B, C, impervious beds below 

and above A, acting as confining strata; F, height of water level in porous beds A, or, 

in other words, height in reservoir or fountain head; D, E, flowing wells springing 

from the porous water-filled bed A.

. ARTESIAN SLOPE.

Fig. 5 shows a section of an artesian slope such as may be found in 

the Atlantic Coastal Plain. The dike shown in the figure, however,

FIG. 5. Section of an artesian slope, a, Water bed cut off by unconformity; 6, beds cut 

off by dike; c, bed in which friction is the only obstruction to downward motion; 

d, porous bed changing to impervious; e, bed pinching out farther to the right.

does not usually occur in this area, although probable instances of 

such penetration occur in Georgia.
REQUISITES OF ARTESIAN FLOWS. 

TJNCONFLNED HORIZONTAL BEDS,

39

The deep valleys occupied by the harbors of northern Long Island 

and some of the deep valleys in drift in northern Michigan present 

artesian conditions similar to those illustrated in fig. 6.

FIG. 6. Section illustrating conditions governing flows from unconfined horizontal 

sands, t, Till; <j, coarse sand and gravel; »/, well.

BEDDING PLANES.

Conditions of artesian flow from horizontal bedding planes, fed 

by joints, are illustrated in fig. 7. A possible example of such conditions is afforded by the waters of the Trenton limestone in southwestern Ohio.

FIG. 7. Section, illustrating conditions of flow from horizontal bedding planes, etc., fed 

by joints. A, Water-bearing joints (indicated by the heavier Hues) ; B, bedding planes 

between limestone and compact jointed rocks fed by joints at A. and B; G, bedding 

plane between shale and compact jointed rocks with local circulation only; D, bedding 

plane fed from sandstone bed; E, sandstone bed fed by joints. .1, Flowing well from 

bedding plane between limestone and compact jointed rocks; 2, dry hole (no circulation along bedding plane) ; 3, flowing well from bedding plane fed from sandstone.

SOLUTION PASSAGES.

Some of the artesian flows of the Vicksbiirg limestone of the Atlantic Coastal Plain and of the Mississippian limestone of Kentucky 

may be cited as possible examples of flows from solution passages in 

limestone, illustrated in fig. 8.

FIG. 8. Section illustrating conditions of flow from solution passages in limestone. 

A, Breccia ted zone (due to caving of roof), serving as confining agent to waters reached 

by well 1; R, silt deposit filling passage and acting as confining agent to waters reached 

by well 2; G, surface d6bris clogging channel and confining waters reached by well 3; 

D, pinching out of solution crevice resulting in confinement of waters reached by well 4.
40 CONTROLLING FACTORS OF ARTESIAN FLOWS.

FROST OR MINERAL CRUSTS.

The conditions of flow from beneath a frozen zone or mineral crust 

are represented in fig. 9. An example is seen in some of the open wells 

that overflow in spring.

PIG. 9. Section illustrating conditions of flow from beneath frozen zone or mineral crust. 

CS, Frost zone or mineral crust formed at"surface of water table when at position 

ACS; B, position of water table under increased rainfall; W, flowing well resulting 

from confinement of water due to rise of head from A to B.

VESICULAR TRAP.

Fig. 10 illustrates conditions of flow from vesicular trap. Some 

of the wells penetrating the traps of the Newark group may be possible examples. -- "

FIG. 10. Section illustrating conditions of flow from vesicular trap. A, Vesicular zone

feeding .well 1.

WEATHERED ROCKS BENEATH CLAYS.

The " lake bed" area, of southeastern Michigan furnishes an instance of the conditions of flow shown in fig. 11.

FIG. 11. Section illustrating conditions of flow from joints, cracks, and solution passages in stratified rocks covered by impervious clays and fed from morainal drift.
REQUISITES OF ARTESIAN FLOWS. 

JOINTED CRYSTALLINE ROCKS. 

41

Artesian conditions in jointed crystalline rocks without surface 

covering are represented by the flowing wells in the granites of Maine 

and New Hampshire and are illustrated in fig. 12.

FIG. 12. Section illustrating artesian conditions in jointed crystalline rocks without 

surface covering. A, G, Flowing wells fed by joints; D, intermediate well between A 

and G of greater depth, but with no water; D, deep well not encountering joints; E, 

pump well adjacent to D, obtaining water at shallow depths; S, dry hole adjacent 

to a spring, showing why wells near springs may fall to obtain water.

BASINS FED BY JOINTS.

Many of the basins between mountain ranges throughout the'arid 

West illustrate the conditions of flow shown by fig. 13.

FIG. 13. Section illustrating conditions of flow in alluvium-filled basins fed by joints. 

1 and 2, Flowing wells from gravels beneath silts, fed from joints that carry water 

from surrounding mountains.

JOINT WATERS CONFINED BY ALLTTvtTJM.

The confinement of water in joints by valley silts, illustrated in fig. 

14, occurs in many of the valleys of the Atlantic Piedmont Plateau.

FIG. 14. Section illustrating confinement of water in joints by valley silts. 1, Flowing 

 hillside well resulting from obstruction of lower outlet by valley, silts; 2, valley well

failing to secure supplies because of action of silts in preventing entrance of water into

the joints.
42 CONTROLLING FACTORS OF ARTESIAN FLOWS. 

JOINT WATERS CONFINED BY SEA WATER.

Fig. 15 presents a section illustrating the action of salt water as a 

confining agent. Some of the low flowing wells near the coast of 

Maine and New Hampshire may be cited as possible examples.

FIG. 15. Section illustrating action of salt water as a confining agent, etc. SL, Sea 

level; A, open joint bringing down fresh .water; B, open joint communicating pressure 

from heavier salt water; TF, well slightly above sea level, obtaining flow in consequence of slight rise in head resulting from slightly greater pressure of water in 

joint B as compared to the water column in the well, due to the higher specific gravity 

of the salt water. *

FOLIATION PLANES.

The section shown in fig. 16 illustrates the conditions of flow from 

foliation and schistosity planes, examples being found in the flows 

from upturned schistose slates in Maine.

FIG. 16. Section illustrating conditions of flow from foliation and schistosity planes. 

A, Foliation plane feeding flowing well 1.

FAULT AND CONTACT PLANES.

Possible conditions of flows from fault and contact planes are 

shown in ideal section in fig. 17. Poland Springs, Maine, presents 

an example of such conditions.

FIG. 17. Ideal section illustrating possible conditions of flow from fault and contact 

planes. A, Reverse fault affording pump water to well 1, but no flow; B, sheet zone 

due to normal faulting feeding flowing well 2 ; C, crushed zone due to normal faulting 

yielding water to well 3 ; D, simple normal fault feeding well 4 ; E, vein affording 

water from contact to well 5; F, dike affording water from contact to well 6. C, E, 

or F, may also be conceived to represent sandstone dikes which may under certain 

conditions become important artesian reservoirs.
INDEX.

A.

Page. 

Air, confinement of water by............... 23-24

Air, confined, pressure transmitted by..... 31

Alluvium, flows duo to, figure showing..... 42

Artesian, present significance of term...... 7-8

Artesian basin, conditions in, figure showing.............................. 38

Artesian circulation, factors in............. 27-33

Artesian flows, requisites of................ 33-42

requisites of, mod if ying factors of...... 37

supposed character of.............. 34-36

types of................................. 37-42

Artesian slope, conditions in, figure showing.............................. 38

Atmosphere, water from................... 10-17

B.

Barometric pressure, effect of, on artesian

circulation...................... 29

Basins, supply of, through joints, figure

showing........................ 41

Bedded rocks; confining agents in....... 20,21-25

Bedding planes, flows from, conditions of,

 figure showing. ; ................ 39

flows from, conditions of, plate showing.............................. 10

reservoir in............................. 10

spring from, plate showing............. 10

Beds; inclination 'of.......................... 35

Blake, W. P., on caliche ................. .'.. 23

Breccia, plate showing....... j............. 14

C.

Caliche, nature and effects of................ 23

Cementation, confinement of water by...... 25

Centrosphere, water from.................. 19-20

'Cephalonia, Sea Mills of, movement of water

at............................... 18,30

Chamberlin, T. C., on impervious beds..... 21

Chemical action, waters due to............. 19

Clays, confinement of water by............. 21

Cleavage planes, plate showing............. 16

reservoirs on........................... ' 15

Confining agents, necessity for............. 36-37

types of................................. 20-27

Converging walls, water confined by....... 27

Cracks, reservoirs in........................ 13

Crushed zone, plate showing.... .......... 16

Crust, waters from......................... 18-19

Crusts, mineral, confinement of water due

to............................... 22

flows from beneath, conditions of, figure showing.................... 40

D. 

Daniel, Alfred, on artesian circulation......

E.

Earthquake, cracks from, plate showing....

reservoirs due to.......................

Ellis, E. E., on joints.......................

Erosion, underground, reservoirs due to... 

F.

Page.

28

Fault planes, flows from, figure showing... 42

openings on, plate showing............. 16

reservoirs on........................... 15

Flows, artesian, requisites of. See Artesian

flows.

Folding, cracks due to, plate showing...... 12

flows from, figure showing............. 42

Foliation planes, reservoirs on ............. 15

Forbes, R. H., on caliche................... 23

Fracture openings, reservoir in............. 13

Friction, confinement of water due to...... 22

figure showing.......................... 40

effect of, on artesian circulation......... 33

Frost fillings, water confined by............ 26

Frost /.ones, confinement of water by...... 23

G.

Gas, expulsion of, reservoirs due to...... 13

Grain of rocks, effect of, on artesian circulation.............."............... 33

Gravity, artesian circulation due to........ 28

H.

Heat, confinement of water due to. 

water excluded by -1 .............

Hoskins, L. M., on rock flow......

I.

Igneous contacts, reservoirs on............ 15

Impervious bed, deformation of............. 32

significance of term..................... 21

transmission of pressure by............ 32

unessentiality of........................ 34-35

Impervious wall, confinement of water by.. 26

J.

Jointed rocks, confinement of water in..... 26-27 

plate showing.......................... 14

Joints, flow from, figure showing........... 41

interruption of, water confined by..... 27

plates showing......................... 14

reservoirs on............................ 13-14

43
INDEX.

L.

Lakes, relations of, to underground water., 17

relations of, to underground water, figure showing.................... 17

Lamination planes, reservoir in............ 9-10

Leakage, effect of, on artesian circulation.. 36 

Lee, W. T., on caliche...................... 23

Lindgren,W.,andRansome, F. L., on joints. 14 

Lithosphere, water from................... 18-19

< M.

Magmatic waters, occlusion of............. 20

Mechanically formed reservoirs, water in... 12

Mineral crusts, confinement of water due to. 23

flows from beneath, conditions of, figure

showing........................ 40

0.

Ocean, relations of, to underground water.. 17-18 

relations.of, to underground water, figure showing..................'.. 42

Outcrop of porous stratum, unessentially

of............................... 35-36

P.

Pervious stratum, unessentiality of........ 34

Pores, original, reservoir in................ 9

Pores, secondary, reservoir in.............. 11

Porosity, effect of, on artesian circulation... 33 

Precipitation, disposal of................... 16-17

Pressure, confinement of water due to...... 25

effect of, on water circulation.......... 33

factors affecting...................J..... 29-33

necessity for............................ 36,37

water excluded by...................... 19

R.

Rainfall, adequate, unessentiality of....... 36

Ransome, F. L., and Lindgren, W., on

joints........................... 14

Reservoirs, underground, types of......... 8-9

types of, plates showing.......... 10,12,14,16

S.

Salt wells, freshening of.................... 18

Salts, dissolved, effect of, on artesian circulation ........................... 30

Sand grains, arrangement of............... 21-22

arrangement of, figure showing......... 22

f orms of, figure showing....... '......... 22

Sands, unconfined horizontal, flows from,

conditions of, figure showing... 39

Page.

Schistosity planes, flows from, figure showing.............................. 42

plate showing....................'....... 16

reservoirs on............................ 15

Sea water, inclusion of, in uplifted beds..... 18

Shearing planes, reservoirs on.............. 15

Sheeting joints, plate showing.............. 14

Solids, suspended, effect of, on artesian circulation.......................... 30

Solution openings, reservoir in............. 11-12

view of.................................. 12,16

Solution planes, flows from, conditions of,

figure showing.................. 39

Stratification planes, confinement of water

by.............................. 21

Streams, relation of, to underground water. 17 

relation ofi to underground water, figure

, showing........................ 17

Surface covering, impervious, waterconfined

by.............................. 26

water confined by, figure showing...... 40

T.

Temperature, effect of, on artesian circulation..........!............... 29-30,33

Tides, effect of, on artesian circulation ..... 32

Underground conditions, description of.... 8-27 

See also Reservoirs, underground; Waters, underground.

V.

Vein contacts, reservoirs at................. 14

Vein fillings, water confined by:............ 26

Vesicles, reservoir in........................ 10

flow from, figure showing............... 40

Water, fresh/confinement of o ther water by. 24

Water, sea, confinement of other water by. 24,27

figure showing.......................... 43

Water, underground, circulation of, factors

in ..................................... 27-33

confining agents of...................... 20-27

necessity for........................ 36-37

density of, effect of, on artesian circulation...........:................. 30

sources of............................... 15-20

Water supply, adequate, necessity for...... 36-37

Water table, local, height of, effect of, on

pressure........................ 31-32

feathering products, waterconfined by.... 26

Wilmington, N. C., salt wells at............ 18