490 MONTHLY WEATHER REVIEW. AUQUST, 1914
7 SECTION II.-GENERAL METEOROLOGY. 55 !* -. I
TEE EXUDATION OF ICE FROM STEMS OF PLANTS.
By Wm. W. COBLENTZ.
[Dated: United Stat= Bureau of Standards, \~aShiXlb$OD, D. V., July 10, l9l4.l
INTRODUCTION.
Nocturnal radiation is generdy a pasirg of radiant energy from terrestrial substances into spacc. On a clear ni h t the rate at which radiation posses outward from
a B ampblack surface is very great, amounting to almost one-tenth of the solar constant. Of course not a11 sub- stances lose heat at this rate. This loss of heat by radia- tion produces peculiar formations of ice, some of which will now be mentioned. Ice coZumn.s.-The most familiar freak of ice formation occurs on bare, clayey soils which contain a certain (min- imum) amount of moisture. If the moisture content of the soil fulls below this minimum value (which no doubt varies for different soils) then eva oration occurs as rap-
action) and no ice is formed. According to t e writers observations the ice is formed in contact with a nucleus which may be a grain of sand, a sniall pebble, etc. The
earthy material has a higher emissivity than the water, it cools more rapidly and thc water freezes on the under side of the nucleus. As heat is lost more ice is formed and, as it accumulates, rises in the columns often to be observed everywhere on cold iiiornings [and techiiicdly known as ice columns or columnar ice]. Tho water IS
supplied by capillary movement in the soil, from the sur- face of which the grouncl ice may be readily lifted, since in freezing weather the ice is not frozen into the soil(1).
The general es erience is to find the ground ice suppork ing a nucleus gay a grain of sand, or even large stones,
3 x lax 1 inch in size). The nuclei may be thinly dis- tributed. The \vrit.er has observed several large areas, 3 x 14 feet, which dit1 not contain nuclei, whence it ap- ears that this ty e of icc forrustion can occur without I a v i y a nucleus &ravel, etc.) to start the refrigeration. Anc or ice.-Bnmes (2) has made a prolonged stuuy of the formation of anchor ice, on the bottom of the St. Lawrence River and frazil or anchor ice within the flow- in mater itself. This kind of ice consists of fine spicules wfich adhere to the bottoni of the river. It forms fria- ble masses which may vary from G to 8 feet in thickness. According to Barnes, this ice is formed as a result of the greater emissivity and hence the greater cooling of the material composing the river bottom. Hoar post.-Another example of ice formation as the
Eere however, the accepted explanation is that the ice spicubs are formed by accretion, as the result of the depo- sition of moisture from the surrounding air. The foregoing are familiar and interesting illustrations of ice formations on substances as the result primarily of the loss of heat by radiation. We have now to con- sider a rarer phenomenon, which is the subject of the present paper.
K
idly as the moisture is brought to t l?l e surface (b capillary
result o f cooling by raclint.ion is the form called hoar frost.
ICE FORMATIONS ON PLANTS.
According to the writers observations the amount of ice formed u on a plant stem is a functiou of- (1) The rate a t whic 1 water can rise by capilltrry action in the sap tubes within the stem; @) the ease with which the moisture can pass out to the surface; (3) the rate of
evaporation from the surface (convection, wind velocity) ;
and (4) the eniissivity of t,lie surface of the stem. Instead of the title Exudation of ice a more pretentious title would have becn The capillary movement of water- An es erimeiital demonstration b means of the forma-
scientific, and one cou ti discuss the capdlary movement of water as a function of the temperature of the stem; the size of bore and number of sap tubes; the thickness and permeability of the malls of these tubes, etc. How- ever, the resent communication makes no pretense a t such conip P eteness of the investigation. In fact, the sub- ject of ice formation forced itself upoii the writer a t a
time when other duties were pressing, and lience it could not be given the attention it deserved. As a result, the esperimental tests, to be described presently, were usu- ally carried out only to the ostent of refuting the various notions held by vnrioua persons as to the cause of this ice formation. AI1 sorts of esplanations were presented. This is the main reason for oiviiig in estenso these simple tests which show that the Formation of fringes of ice on plant stems is not the result of accretion, hydrostatic pressure, rifts in the stein, nioi3t8ure in the barb, the res-
capillary movement of water in the numerous sap tubes which are to be found in those plant stems upon which the ice formations are the niost conapicuous.
Historicab datu.
One of the earliest descriptions of the exudation of ice fringes from plants was published by Iierschel (3) about
SO years ago. His obuen-ations relate to the icy fringes which were formed around thistle stalks and stumps of heliotropes, many specimens of which were still green. Stephen Elliot (4) had reviously described a remarkable rotrusion of fringes o P ice from the stems of flea bane
The fullest account, with an attem tod explanation of this phenomenon, was given by John E e Conte (5) about
03 gears ago. His observations are on two species of flea bane, PZuchea b$ron..s and Pluchm cn~fiyho~ata, which he found growing in wet soils, around ponds, and alone roadside ditches in the lowlancls of South Carolina an8 Georgia. In these lants the root is perennial, but the
Le Contes descriptions differ materially from my own. His observations appeared to establish the following facb in relation to the phenomenon:
1.
The depositions of ice are entirely confined to the immediate nei.rhhrhood of the roots of the lank the u er parts of the tall unbrokan Rtalka being quite free torn &em. !Key frequently com-
f
tion o f ice fringes on lants. T&s might appear mme
ence of sap, etc., but that it is the result primarily o F the
pr!Owy zu bqrons).
stem is annual and i erbaceous.
AUGUST, 1914. MONTHLY WEATHER REVIEW. 491
mence 2 or 3 inches from the ground and extend from 3 to 4 indit*s along the axis of the stem. The stalks are dead and quits dry to withiii about 6 iiiches of the earth, below which they are genenllv green and succulent. The plant has a large and porous pith, which is alway~ saturated with nioiature as high as 6 or 7 inches from the base of the stem.
From this it would appear that the ice was formed on the green stems, as was true of many of the specimens of heliotrope described by Herschel.
2.
The ice einanstcs in a kind of riband. or frill-shaped, \mvv, friable, semipellucid excres1:cnce. the structure of which (quoting Berschel) is fibrous, like that of tlie tilxous variety of gJpsum, presenting a glassy, silky, wavy surfwe; the direction of the libers being at rielit anglea to the stein, or liorizonhl.
Le Conte found that the number of ribancls varied from one to five, which issued from the stems in vertical or longi tuclinal lines, of ten unsymmetrically displayed around the axis. He frequently observed the icy exnres- cences to escecd 5 inches in leilath; often curled back so
that the remote extremity of &e frill came close to the line of attachment to the stalk. From this it may be noticed that the amount of ice formed is very considerable. Evidently the moisture must come from within the plant. The amount of waiter congealed during a single night is vast.ly too great to come from the aqueous vapor in the atmosphere; hence the phenomenon can not be a nioclificstion of hoarfrost. In fact, in the illustratioas to be cited presently, mhicli were observed by the writer, the escrcscences of ice on one particular species of plant ivero fornietl ever night that was sufficiently cool for ice forniation, :iLiough there was little or no forniation of hoarfrost snywvlicre in the riciniby. 3. Although the ice sheets appeiired to protrucle from the interior of the stern, both Herschel and Le Coiite found that usunlly the stcnis were solid nntl thikt the ice terminated at the surlrrcc. The point of attachnieiit of tlie ice was :blways the wood, beneath tlie outer bark or epidermis, which the frozen sheets Bad in every instance stripped off and forced out to a distance. When the frost was severe Le Conte found that the ice riband was continuom with the frozen pith through a longitudinal rift in the woody stem.
4. Le Conte found that-
The phenomenon took place in the same plant during e e w d con-
sccutive nights, and, when tlie wood was not rifted, frecpentiy froin the same portiun of the stalk. Wlie~i the wood was split, hwe\-er, the depositioii of ice orcurred lower down the stem at n part whidi was unalfected b tlie frost of the previous night. The skilka thus became coinplett-& rifted by a succession of severe nichts f r m i the height of 6 or 7 inches down to tho grouud. This is unquestioinl~lv one of the rwwns why these exudations of ice are aeliloni otmrved a h r the middle of the winter, for tlii: stalks are usually destroyed before this period.
Le Conte considered the ice formation on plants to be
a physical plienomenon, having no connection with the vitality of the stein. His esplanatioii of the ice fornia- tion was that the moisture from tlie pitli passes out nlonm the wedgeshaped niedullnry ra s which me to be founa in abundmce in this plant, nnc i? is frozen on the outside of the stem. He considered that, the wedge-slieped med- ullary rqx eserted a projectile force which brines the moisture to the surface. The esuclstion of ice coTumns from the earth lie referred to the smie cause, viz, a rapid and forcible espnusion, along ctipillary tubes. To the writer it does not appear necessary to )ostulnte
plants. In P act, the plaiit,s upon which ice is formed in the greatest abundance have a preponderance of sap
a complex  roject.ile force to esplain the ice f l ringes on
tubes, only an insignificant part of the stem being occu-
pied by medullary rays. Ward (6) has given a rather popular description of the occurrence of ice fringes. He describes the fringes as ro- jecting out horizontdly, not straight and stiff, %ut gently and gracefully curving or coiiiiig into a beautiful
concdike roll a t tile distal end. iiis observations were probably of short duration, otherwise he would have found but few instances in wlLich tlie fringes are at- tached a t regular intervals mound the stem, like paddles of a turbine wheel. He found tliiit the bark was split into strips a t the zone occupied by tlie ice sheets. He concluded that the ice had passed through these rifts in the bark. He thought that tile water might have been
pressed or drawn up tlvougli tiie cambium layer. He wisely dismisses the esplaiiation because it  explained too much since no re~son can be assigned why the phe- nonieiioii should not be universrrl and iiot codined to one
species (7). In the present paper micropiiotograplis of the cross sectioiis of various plants will assign this rea- son, viz, the cliflereiice in the porosity of the stems.
Recent Data..
During the f a l l and winter of 1013-14 (which may be cilled mi open one in that t,lLcre wits no snow until after Dee. 1, 1913) tlte writer liud been walking daily t,ltrougii Hock Creek PwB, on his way to and from tlle
Uiiitecl 8t.cit.i.a Uureuu of Stndilr&. Tlte route is alon tile  Beach driveway which winds alung the east ban of the creek. lllis driveway is bordered by D steep hill- side, from 10 to 5U feet iti heiglit, \vliicli is thinly cov- ered with secoiid-growth trees, tile majority of wliicli are
ouks i~nd beeches. There is a tliin undergrowth of grasses and oi various iierbaceous plants with annual stems and pereitnial roots. From this it may be seen that the linbitat of the plant about t u be described is different from the one mentioned
by Le Conte, wliicli thrives on wet soils. Tiie present observations iire oil Oiirda mwimcc or Dittnny, wliose steiii is an lierbllceous aiiiiutil with peremid root.s. This p+int seems to tlirive on dry ground, even on bare ldl-
sides esposed to tlte blazing sun, where there is nothing but gravel and n few sster~.~ Other samples were found under trees where either the shade or tlie gravelly cliarncter of t,iie soil prevented a luxuriant growth of other plaiit,s. Tile finest samples were found on ~t hillside wliich contained plenty of moisture and was free from trees, but contained slirubbery. Tiie first obserntions were made on a frosty morning in November, 1913. The first example, because of its w1iit.e ribbony character was passed by, thinking it was something thrown from a passing carriage. The con- spicuous white fibrous loops and ribbons drew my atten- tion, a1ic1 it was at once observed that they oc.curred upon only one species of herbaceous plant. A sample of the plant was sent to Prof. Cleveland Abbe, of the United States Weat!ier Bureim, wlio pronounced this a rare and an interesting observation which should be followed u by 2% more tltorougli study of the ice formations. Wlii P e tile probleni itself seemed a very interesting one in radiu- t.im and in the capillary movement of water, i t never- tldess seemed an intrusion upon my regular program
of rdintitsn work, so that a t first but little attention was given to it, other than scattered observations in passing to and from the bureau. As time passed, many diverse opinions were received as to the cause of the ice forma- tion. This called forth additional testa so that the a p e -
E
492 MONTHLY WEATHER REVIEW. AUGUST, 1914
rimental data now at hand are rather voluminous. In view of the fact that memory is treacherous nates were taken in the field a t the time of observation.
Owing to the pressure of other problems requiring close attention, the very first impulse was to dismlss the sub- ject by accepting Le Contes esplanation that the moisture comes from the pith. This explanation was at once dis- proved, however, b the observations on the s l i t e r s of
of the stem, but never on the pith. This, of course, should be ex ected for pith is composed of small hexa-
attraction and it would be very unlike1 that it would be
is somew % a t angular, especially as viewed with the bark
on, havin a cross section of 1.5 to 2.5-mm. The height
plant stems are very fragile owing to the structure of the stems which contain but little mood fiber. The plant is also weak in structure owing to the eat amount of ith
the pith is arranged in the steni. As shown in figures 1 and 12 the stemis some- what rectangular inoutline, the pith bving a similar shape, but the corners are rotated 45. At these corners of the ith there
the pith and the bark, and it is along this line that the stem often cracks. Per- haps this is the reason for the ersistent belief amon
with -. the phenomenon that
the Cunila stem, w&ch formed ice always on t P le outside
hedral cells a P ong which water can not pass by capillary
transferred by soakin throu& the cel 9 walls. Desk tion of the p %! nt.-The stem of CuniZa mariana
of the sta Hk is from 25 to 30 cm (about 1 foot). The
and t f e manner in wiich f /BARK
is but little woo a between
8 the F ew who are acquainte
._
Fut. l.-Diagramrna+ cross Section of stem of Cuntlu muriano.
the ice ribbons come from these rifts in the stem. The small stem, weakened by splitting, is an easy prey to the wind. Photogra lis were taken of thin sections across the stems of he l otrope,. thistle and also of an aster which waa found near a Cunala stalk. The object of these photo- microgrn hs (which were very kindly re ared by Mr.
have but few sap tubes an which form little or no ice fringes; also typical esamples of plants which have numerous sap tubes and which form an abundance of ice fringes. The aster is typical of plants having but few sap tubes. As shown in figure S the woody struthre is very compact with but few sap tubes, All these microsections are magnified 50 times; thus one can obtain some idea of the great difference in porosity of the different plant. On only one occasion was ice observed upon the stem of the aster. The ice was a small tooth formed close to the ground. From the section shown in figure 8 it is evident that the structure of the wood fiber is so close that the moisture, which is drawn up within the stem by
cn illary attraction, can reach the surface of the stem at
eva oration as rapidly as it comes to the surface. &e thistle (fig. 9) and the heliotrope (fig. 10) stems have numerous large sap tubes. In the thistle stem there is a row of lar e tubes situated near the bark. The pres-
formation of ice fringes as observed by Herschef
P P T
E. D. Ti if yer) is to show a t ical esamp e o plants which
o s y a very slow rate. Hence the moisture disappears by
ence of these f ar e tubes filled with sap may ex lain the
Photomicrographs of thin sections of Cunila are shown in figures 11 and 12. The numerous holes in the wood are the sap tubes which form an eas path for the
It would be interest to determine to what extent this
ture of the surroundings. The explanation of the formation of the ice fringes found to occur so abundantly upon the stems of CuniZa
and which are not found upon other plmts, is based upon the presence of a great number of closely adjoining sap tubes within the stem of the Cunila. But even the very woody portion of the base of the Cunila stem was found to be inactive in the formation of ice fringes. It was found that the ice fringes rarely start from the side of the stem where the pith is closest to the bark. This eliminates, to some estent, the question whether the pith is instrumental in forming the ice fringes. In the splinters and in tlie rifted stems of Czmnila, at no time was ice found to have formed along the line of separation of the stem. This seemed puzzling a t first, for it appeared to contradict the idea that the moisture comes from the sap tubes within the stem, in which case one would espect to find the formation of ice fringes facilitated upon the surface laid bare by splitting. The microsections of the CuniZa stems show in a very unexpected manner why no icc fringcs are formed upon the rdted surface of the stem. As already stated, the rift alwa a occurs a t the corners of the pith where the
noticed in figures 11 and 12 that a t the four points where the wood is the thinnest there are usually but few, if any, sap tubes. Hence one need not expect to h d ice formations upon the surfaces formed by Splitting.
Field and laboratory observations.-The field observa- tions were made on isolated plants found scattered throughout the woods; also on three test beds of lant stems without their roots, which were convenient f y lo- cated along the roadway. The first test bed Test No. 1  was planted January 7, 1914, with lant stems 10 to 15 cm. long, which had
test contained: (1) A stem and branches with bark intact; (2) a siniilar stem with two costs of shellac varnish; (3) a stein having the bark thoroughly scraped from one side and the other side shellacked over a length of about S cm.; (4) a stem scraped on all sides and the one-half of it shellacked; (5) a stem having linlf its circumference scraped, the other half having the bark intact; and (G) a stalk planted head down. The loca- tion proved to be a poor one, the ground not retaining moisture. The place was disturbed, but in spite of this some results were obtained. Tests No. 3 and No. 3 were planted on January 11,
1914, and consisted of about two dozen plant tops and stenis which had been broken off by the wind. They were placed on a gravelly bank which was not desiccated by the wind and sun. Some of these stalks wcre covered with soil up to their branches. In none of the field tests were tlie tops of the stalks covered to prevent deposition of atmospheric moisture. Test No. 3 con- tamed several stalks of heliotrope and stems of wild grapevine which, of course, at this late date were entirely dead. As already mentioned, Herschel found ice frin es on the green stuin s of heliotrope. At no
wild grape steins which were green). Special note of this fact was made on January 23 and February 2,1914.
moisture to rise within the stem, by capil 9 ary attraction.
capillary movement 4F; o water is affected by the tempera-
woo B y part of the stem is the thinnest. It may be
been in the B aboratory since November, 1913. This
time di 5 ice fringes form on t R e heliotrope (nor on the
FIQ. 8.-Cross section of stem of aster, show' compact woody structure and few sap tubes. Magnific%fon 50.
N
sap tubes. Magnification 50.
M. W. R., August, 1914. To face p. 492
A
- .a. 10.- - V.Y.V.. ". llvy Action of stem of heliotrope, o.ldwing numerous sap tubes. Msglrlncation 50
AUGUST, 1914. MONTHLY WEATHER REVIEW. 493
The laboratory tests started on January 30 and were made on plant stems laced in a receptacle containing
the samples were mounted in a small porcelain crucible
as shown in figure 2. The plant stems were fastened into a piece of heavy cardborird by means of Khotinsky cement. The cardboard was then covered with p a r a 5 on both sides and secled with parafh to the top of the crucible. A sniall pinhole e ualized the air pressure,
The rotruding stenis were covered with a glass beaker,
Two additional laboratory tests were made on plant stems placed, in test C, in a test tube, as shown in the hotograph, figure 19; and D, in a wide-mouthed bottle. fn all these laboratory tests the stems were covered to prevent deposition of atmospheric rnoi$ure. Experiments showing how the water 2s conveyed.-The field observations, Test No. 1, showed that the water is not transferred along the cambium layer or the bark. Ice was formed on that half of the stem which was scraped, but none was formed upon the art (whether scraped or unscraped), which was covere B with shellac. This observation was confirmed on different occasions, special note of this fact having been made (test 1, speci- mens 3 and 4) on January 8, 12, and 27, and February 2
and 3. In specimen No. 2 of this test the ice forced out the shellac at the juncture of two branches on Feb- On these dates (as well as others which it wou d be too tqdious to record in this paper) my notes show that ice fruiges, large and small, were formed u on numerous plants contained in the plats describec? as
tests 1, 2, and 3.
The laboratory tests A and B showed that starting with stems that had been drying for nine weeks in the laborntory the moisture is transferred ve rapidly after placi the stems in water. In test ATee fit 2)
four scrap3 samples were thoroughly covered wit an inipervious cenient at the point of contact with the card- board C. About 2.5 cm. of the stems estended above the support. The next morning (Jan. 30) two sam-
p h l y soaked The were from the upper part of the p ant, hence ihin-wa f ed and less ples were found thoro
woody. The third sani le, which was taken from near the root, was inactive. !&e fourth showed slight mois- ture n t the to and by night (34 hours in all) this sample
The second laborntory test, B, consisted of the two most active samples of test A thoroughly dried and covered with cement, K, as shown in figure 2, and placed in water containin a red dye. The sani le a was covered
at the sides. The sides of the ininiersed part of this stem were covered with cement, so that the water would have to traverse the sap tubes in order to reach the top. The immersed end of snniple 6 was covered with cement,
so that the water would have to soak in through the sides in order to traverse the stem.
3, 1914 (uncolored), moisture was observed on the bi es of a, and the top of b showed the red dye. Evidently thc water had traversed the stems to a height of about 3 cm. b ca illary move- ment. In tho subsequent tests, C and%, d e stems were more than 6 cm. in length, and it was found that the water rose to a height of 5 cm. However, when uncovered and exposed to the wind the moisture did not rise higher than 1 cni. to 2 cm.
water. In the first an( P second laboratory tests, A and B,
thus preventing any possib P e hydrostatic pressure.
whic E prevented deposition of moisture from the air.
3.
was thorough r y soaked.
at the top, K, so t f lilt the water would me to come out
FebruY
The next morning,
that the water required for the formation of ice fringes comes from within the stem, and that the fringes are not caused by accretion or sublimation as in hoarfrost. One of the observations a plicable to this question was niadein
elsewhere in this paper. The niorning following the for- mation of the ice fnnges on the Ch.mila stems it waa ob- served that considerable water had disappeared from the glass receptacles. The glass beakers covering the stems were perfectly clear, showing that no water vapor had condensed (and frozen) upon them. Evidently the ice
connection with the 7 aboratory tests, C and D, discussed
F~Q. 2.-Arrangement of lant stems ln laborator testa A and Khotlns%y cement, Cpara5iu-Ted cardboard. B. K aeabg of
fringes had been formed from the water that had disap- peared from the glass receptacles. Another observation (January 6) was on a plant in the woods, surrounded with green moss and well covered with leaves of trees. The stem had several large ice fringes that were hidden by leaves. The leaves were covered with hoarfrost. A very convincing field test was made by painting the stems with asphaltum in turpentine. If the ice forma-
tions were the result of condensation of moisture by rapid cooling, then the black paint should have ice formed upon it. In the afternoon of January 13 (the ice fringes having nielted as usual) a number of CuniZa plants free from bark, situated in various parts of Rock Creek Park, were given a coating of asphaltum paint. Test No. 3, mentioned above, contained several painted stems. As shown in the photo-
graphs, figures 15-18, the outer edge of the ice fmge is smooth, which could hardly be the case if the formation were similar to that of hoarfrost. 97 it was
found that on two plants in test 2 ice fringesycd pushed out the asphaltum varnish which was found adhering to the outer edge of the ice, 1.5 to 2 om. from the stem of the dent.
On Jnnua
r- ----
Fwther tests sho&ng t7uzt the water comes *om within the steww-There are several observations which indicate
In test 4 the ice had pushed out the asphaltum and had formed a fringe in the rent in the paint. For some days
494 MONTHLY WEATHER REVIEW. ATJQUST, 1914
subse uent to this date there was no freezing weather, but on Fetrua 3 other s t a l b were found in which the asphal-
edge of the ice fnnge. be added that for some
of ice fringes seemed to be mhibited. The field tests (test 1) described above, pnge 402, in which one side of the stein was covered with shellac varnish, showed t.liat the nioisture was not conveyed from the ground upward along the outside of the stem. In view of the fact that the bark is often found pushed out by the ice, these tests with asplinltuni seem supcr- fluous; but the persistent presentation of the hoarfrost theory to account for this ice forniation, seeined to re- quire a reductio ad absurdum test, The mere fact that hoarfrost has the forni of fine spiculrs while these fringes a.re smooth should be sufficient evidence to dis rove the
cause then the black aint, with its high emissivity
of hoarfrost u on the outside of the paint. The ice fringes
sufficient1 low to cause freezing, whether or not there
formed is f n r in excess of what sceiiis possible by the 1io:ir- frost theory. (See the photographs, figs. 13-19.) On January 7 the ice fringes formed on a smgle plant were collected and weighed. The ice formation on this plant on this date weighed over 5 grams. The weight of the ice on the lnge saniple shown in the photograph, figures
15-19, is probabl between 4 and 5 grams.
superfluous to remark that the ice fringes nre not coin- posed of the plant juices. The ice is tnsteless, in spite of the fact th:it thr plmb hns n strong frngrance of tliyii~ol. Observations 8howk.g hour the ice f?<nge grozcs.-(he of the most biteresting observations was the foriiiathn of the ice fringe froni its ve beginning. This was wit-
verify the observations. On the cold Iiiorningl of Feb- ruary 16 the samples in test B were placed outside the laboratory window and in about 30 minutes the ice fringe was observed to be forming. It consisted of a row of fine hairs estending up and down a length of about 4 mm. of the stem and proecting horizontally 0.2 to 0.3 mm.
viewed against skylight, and they nieltecl ininieclintely on lifting the glass cover. The fringe did not, appear to forni a t the lime where the >ith is closcst, to tho surface of the stem (see fig. 1). Tliis e.xpe.rimmt wns rspented a h during the evening. Within half a.n hour after
the cofd air one stcm showed several fringes in t io forin of thin transparent teeth,  each one being about 13 112111.
in length and about 1 nini. in height. hinther steiii showed a fine hairy fringe which wns visible when viewed against a gaslight. Within half an hour this hnirg fringe appeared to be solid, with sonie of the fine hairs eskndiiig
tum varnis 3 was pushed out and adhering on the outer
days after applying the aspha r tun1 paint, the forniation It nia
hoarfrost theory. If subliniation by cooling ha c f been the
(Lcooling power) shou P d have produced a great arnount
were alwnys P ormed on nights when the temperature was
was hoa I-? rost in the vicinity. The actual an:ount of ice
In view of the 7 act thnt the stenis are dry it is of course
nessed by several of my col 7 eagues, who were calleil in to
(See flg. 3, A.) T ! iese filainents were visilile only when
p P acin the saniples (test B with a.dditimn1 sn.m des) in
11
- - - - -. -
1 The thermograph (altit. 62 feet above street) at the Weather Burenu recorded the follow&& temperatures durlng the forenoon 01 Fcb. 16,1814:
horizontally outward through the solid tooth of ice,
as shown in figure 3 B. This, of course, is the gen- eral structure of the fringes. By tlic nest iiiorning nunicrous wide fringcs had fornicd on these stems. In another sn.mple the tooth of ice pushed out a narrow strip of bark siiiiilnr to the illustration given in figure 3 B. In those tests the rcccptacle containing the water WRS sniall, hence the whole cooled very rapidly and the watcr froze, thereby preventing tlie growth of the ice fringes. It is to be noticed thnt tlic ice fringe forms smie distn.nco u the stem, n t n point wlierc it cools the the nioisture has risen to about its nin.simuni hcigh t. Test C started February 17, enibrnced half a dozen samples of Cmila. and a stcni of nn aster in a largo trst tube. The test tube was embedded in wool to retard
quic.kest irnd wiere P
U
A. B C.
FIG. 3.--Stages in the growth 01 the ice frin<e uudor the esperimentd wndltlons of figure 1.
coding a.nd freezing. Within 15 iiiinutes after placing this :~.~~rmg:crment I utside tho lnbvratln-y winditw, two sinal1 fringes 1.5 ?iiin. hmg nild nbuut 0.3 iiini. high were iii?ticed when vicwcd ngikst the skylight. This test
was I~rolongccl for some days and nights. On February 1.3 it was plititl-bgn )lied (sco fig. 19) t n show that ice fringes f m i i as rtw i ily wlir\n the stems nro in water as whc*n they a.rc attitchod t r l tlir! routs. In this photogaph, w1iic:li is i~agnifiecl slightlyv, nbc;ut c,ne-third of the upper part of the largest fringe is lm lwn c t f f . Ihcsc fringcs a.ppenr n little inore I maspnrcnt thnn usunl, owing to mclt- ing while taking tlic plir:tr-pqh. No icme c!r nusisturo was ftms.ec1 on the aster stem. This ngrces with the field clbservilticns, which furnisb cmly cine instnnco where there wns an ice fringe found upcm an aster @ern. In this fiold sniiiple of aster there
wxs but little ice, which wlis very clwe to the ground. In tcst C all the QmiZa stems showed moisture, and ice
wriis f m w d on nenrly all of them. The t h k e s t steins fnrniocl the nilst ice. Test D, started February 17, consisted of an nssortiiient of 10 C$i,tj<ih. stcms nwunted in R lnrge7wide-i?ir~utlie~l bottle lxwing R capacity of about 1 liter. Tllis bcttle, wrapped in hair felt, wns plncecl in a box kept nusiile the labora-
tlie carcl1)c:uwd lid, which TVLW tliorc:iuglily covered wit TI
ttwy whidciw. The steilis were supp*wted as usual b
p ~n f f i i . The protruding steins were covered as usual with a large glass beaker, which rested closely upon the felt.
AUQUST, 1914. MONTELLY WEATHER REVIEW. 495
As may be seen from figures 1, 11, and 12 the CtUnilcG stem on drying (shrinking) splits easily into four parts, owing to the sniall amount of wood fiber a t the four sides of the stem. One of the samples used in test D was a splinter, consisting of one-quarter of the stem, about 6
cni. in le th, with a line of pith adhering to the inner
this splinter showed a fringe o ice on the woo 9 surface, but a t no time was there ice formed on the pith. One sample consisted of one-half of the stem as shown in figure -4 A, and on February 20 a solid fringe or tooth of ice was found projecting out to a distance of 34 mm. It was about 2 mm. wide a t the base and extended er- haps 1 cm. along the stem. An interesting feature (wlich to the writer became a common observation) was that t.he ice fringe did not always start a t the corner of the stem where the wood is the thickest; neither did it start
?3 side. On a t e following niorniy and on subse uent days,
A.
E.
in fi ure 3C. This seems to be the usual manner in
the stem, however, does not seriously affect the ice forma- tion, ns may be noticed in the ncconipanying photo- graphs. One saniple had n fringe 3.5 ciii. in length and
2 to 3 nmi. thick at the bass. When thc bark is still intact, the ice forination appears to occur most fre uently at the corners of the stem. (See fig. 1.) In t % e bare stems thc ice was sometimes found (test D, Feh. 17) to be formed well around the stem as shown in figure AB, mid nuinerous field observations showed that this is the result of the fusion of two fringes, leaving a wedge-shaped free space between them. The coninionest form is shown in figure 4G (field observations of Jon. G and S), in which the ice ribbons were described as a composite of thin sheets which were estimated to be 0.3 nini. ui thick- ness. The open space was perhaps 3 mm. wide at the
whici 7 the stems are stripped of bark. The bareness of
s. c. D.
:-
FIG. 4.-FOnnS and positions assumed by the Ice fringes on Cunila stems.
at that art of the stem where the wood is thinnest, but
micrograph of a thin section of the stem it appears that the largest part of the ice fringe niay form at the point whore the sap uubes lie neares! the surface, hence where the moisture can be most easily supplied. Another sample in test D consisted of L thin stem (1.5 mm. csoss section) which was split into four segments for
a length of about P cni. The ends of the stem were intact. My notes, rccordetl nn the morning of February 20, state:
One can see through the cracks in the stem. Two ice fringes are formed, extending outward to a height of 7 rum. and extending 12 mm. vertically dong the axis of the stem; but t h q are notfonnedQ the cmeks.
In fact, the point of attachment of the fringe to the stem, as esaniined u d e r a reading glass, did not even extend close to the cracks. In some of the sani les in test D the stems were entirely free from bark (see t R e photograph of test C) while some were covered with bark. In the latter Sam les the ice
a t a mi K -point as shown in w e 4 A. From the photo-
pushed out a narrow strip of bark 1 111111. wi a e, as shown
base. The base appeared to be n solid shell 0.5 nlm. in thickness. One could eitsily look through this wedge- shaped opening. Sometimes these fringes adhere well to the skni so that the ribbon breaks across the open s ace.
esplnins the ease with which the ice ribbon is usually separated from the stein. The bare stems used in this test were old stalks from which the bark had been sepnrntecl by previous ice fornip- tions in the woods. Evidently thc laborntory tcst did not interfere with the ice formation. The roots are not necessary for the production of the ice fringes. As (t
matter of fact the stalk t m d the neitr-by roots are de$ nlthou$i the rest of tho plant (new growth) is perenninl. The ice usually formed on the flnt side of the stem, but,
as already mentioned, it often WRS found to cover the whole side, as shown in figure 4B. In some stalks the ice toothJJ was found (note of Feb. 17) to ha.ve fornied near the corner of the stem, as shown in figure 4 6 .
Other ice teeth were observed in process of formation, as shown in figures 4E and F, the ice being solid, about
After sunrise the stem warnis rapi!lly, w!iich no s oubt
496 MONTHLY WEATHER REVIEW. AUGUST, 1914
3 mm. in length and half a millimeter in height. Figure
4E is observed on test B, February 13, and figure.4F was found in the field on January 11, 1914. Since it is gener- ally believed that the sterns are split by the frost, it is
important to notice that in these laboratory tests none of the stems were rifted by the ice formation. The rifted stems used in these tests were sani les which had cracked on drying and shrinking, after laving been in the laboratory. The ease with which these stems became saturated with water after having been drying for weeks is another item worth noticing. All the stems used in tests C and D had been in the laboratory for some time. Some of them had been athered in November, 1913, and had
It is generall su posed that the ice is formed more been freed of bar a by previous ice formations.
easily in the fa d % (w en the plants are fresh) than in the
A.
C.
started the previous evening. Test D had ice fringes on 7 of the 9 stems of Cunda. The thick Cunilu stumps did not seem to be able to form ice; and there was no moisture on the outside. Test C had ice fringes on all the 4 Cunila stems, but no ice or moisture was on the aster stem. The aster is one of the common plants found grow- ing near some Cunila stalks, but was so badly broken t,hat it waa not identifiable wit.h any of the numerous asters which abound in the locality. Some stems had 4 fringes, but no ice was observed in the cracks which were in one of the stems. Sonie of the fringes were curled back against the st,em. Test B showed ice fringes on two of the three stems under observation. The third stem was a very thick one, which showed a fine line of ice just starting. The fringes were small, being only about 3 mm. long aud 2 to 3
mm. high.
B
D .
N O
JOIN T
rt
Pro. 5.-Forms and pollltiona asaumcd by the Ice rrtnges on Chila stams.
late winter. This seems to be true, to some extent, according to my field observations and my laboratory tests. In tests A and B the ice did not seem to form so abundantly after the stcnis had soaked for some weeks,
as though the sap tubes became clogged or the plant had begun todecn .
February 21, no records were kept, and at the risk of
being r( liu the notes of the last two mornings, February
20 (warm and rainy the first part of the
fringes were found esterding 2.5 to 3 cm. up the stems. Test C contained 5 Cunila stems and one aster stem, ice fringes were found cn 4 cbf the 5 Cunila stems, but no
ice or mc isture was found on the aster stem. l here were
2 to 4 fringes on each stem, some of the fringes being 1
cm. wide, i. e., extending outward horizontiilly 1 cni. from the stem. Ihe last laboratory obaervatirns were made on the morning of Februa 21, 1914. 1 ests B, C, and D were under observation, 3: aving, of course, been
Although t E e laboratory tests were continued after
20 an B 21, are given herewith.
night, cold an T freezing in the mornii g ) moisture and ice On Februa
The peculiarity of the fringes on Fehr~~nry 21 was that in nll three tests (B, C, and U) the frhges were siiiull and t,he outer edges were cun-ed b d i npimt the stem, as
shown in figure 5A. lhis seems an iiiterestiiig obser- vation frrr it serves to esplnin the peculiar ice loops so
lhey no doubt start
as n thin ringe (as in the laboratory test of February 21),
one side of which grows f d e r than the other, thus forrn- ing a curved fringe (see fig. SA), which in some cases srenis to freeze against the stem. As more ice is fornied the loop is merely enlarged, as in figure 5B, w l d i is a
field observation (Jan. 18, 1914) on a rifted stem where no ice was fcrmed in the rifts. I his loop was jointed at the ends. A still more remarkable fornintion (observed Jan. 18, 1914) is shown in figure 5C, which also showed no ice formed in t.he rift. In this Sam le it was especially noted that the Iocq was not jointecr A further illus- tration r f the crlmposite character of the fringe is shown in figure 5 0 (field ohservntim Jan. 181, in which one side of the fringe has intermittently grown faster than the other side, thus forming a wavy, fluted surface, while the
observed in the field.
AUGUST, 1914. MONTHLY WEATHER REVIEW. 497
other side is smooth. My notes of January 1s state that the loop is usually jointed at the outer edge (fig. 5B), the fringe usually starting near the rift. These illustrations seem tn indicate t-hat the ice fringe heqins as a row or several rows of fine, hair-like, filaments
of ice, as sh(.wn in @ure 3A. These filaments nf ice, which reinincl one of the finest fihments of mold, in- crease in number, fill in tho gaps, and form a continuous film (I f ice. They estentl upward and downward along the axis of the stem, aid they widen out, .thus producing wedge-shaped formation of ice which one finds the in t e early stages of ice-fringe growth. sible that when the ilant is e s osed in the open fie ds,
stnge r:f the ice fringe are not formed aid that the thin solid, too th-like formation constitutes the beginning of the ice fringe. As shown by the laboratory test, how- ever (test B mentioned on a previous {.age), the ice fringe pttssed through both stages of growt At 7 p. in., February 16 t h e h e hair-like filaments were visible. At 7:30 p. m. theso filaments had multiplied and coalesced into a solid film with hairy streaks in it, as illustrated in figure 3B. The following morning the fringe had grown larger than the sample shown in the photograph of test
1 hese laboratory tests serve to esplain the filamentous structure of the mature ice fringes. They are always found to be fibrous and the ice ribbon often breaks into scveral ribbons. This is well illust.rated in the large ice fringe shown in the photograph of test C (fix. 14). The light horizontal lines show the edges of the individual fnnges. In fact this particultm sample contained lrirge open spaces, in spite of the faLct that it was not more than 3 mm. in thicknesr, i. e., the thickacw nf the stem. The formation of the ice filaments (figure 3A) might be regarcled as evidence sup ortin Le Contes theory of a
projectile force whici F % pro uces the fringe. Then arises the difficulty of finding the cause of the  projectile force. The physical forces now familiar to us seem sufficient to account for the phenomenon without invok- ing unknown forces. These known physical activities are: (1) Cooling by radiation; (2) a ra id ca illary move-
sufficient moisture in the soil, so that the capillary forces can bring moisture to the surface at a greater rate than that at which moisture passes into the air by convection and by evaporation. The capillary movement of water may possibly be accelerated by the temperature gradient in the stem, which is cooler on the outside. The main difficulty i n thi3 explanation of the cause of ice fringes lies in the fact that the second stage in their formntioii is an apparently solid wedge of ice (see, however, fig. 3B), whereas the mature fringe IS fibrous in structure, very friable, and often separates into a series of wide
in air tem erature, by evaporation, eto., which produces
tory formations never appeared quite so white. The great transparency of the sani de, test C, shown in fi ure
field specimens differ greatly in translucency. n a cold frosty cloud morning (Jan. 18 a ), the atmosphere having
a dam  Leling, the nunierous ice ribbons, 2 to 3 cm. in lengt& were cons icuous for their great transparenc .
stemP-TIie ice fringe is usually found to ad ere oosely to tho stem. It seems to continue to increase in size even when the ground surrounding the plant is frozen to a
It is YS- the fine, httir-like fi 1 aments w R ich constitute the first
c (fig. 19).
ment of water through the interior o P P the p ant; and (3)
ribbons as thin ns tissue aper. This fibrous structure, however, may be the resu of reformation by variations
the white F rivge shown in the photographs. The labore
19, is owing to melting while ta 1, -ing the photogra h. $he
f Wlat determines t 5, e location of the ice f+in e u on t e
8
lx
depth of 1 to 2 cm. As Le Conte found, the ice formation ceases its growth after the ground has become frozen to a considerable depth. The moisture in the stem is then found to be frozen, and ice is found in the (rifted) stems. On very cold mornings the ice fringe estencled down to the ground (observation of Jan. 11). How close the fringe approaches the base of the stem de ends, of course, upon the temperature of the ground. g i e height to which the fringe can form seems to be governed by the rate of capillary movement of the water, and the rate of evaporation (and convection) from the surface. In my laboratory tests where the plants were covered and pro- tected from the wind, the moisture rose 5 to 6 cm. in the stem; but on removing the cover evaporation reduced this height to 1 to 2 cm. Wlien the soil was wet the ice ribbons were the widest. For esaniple, on Jantiary 7, a width OF about 4 cm. (1% inches) was recorded. After several d a p of cold and freezing, the ground having become quite dry, the ice frill e m s short and did not
dence that the ice fringe may form on a definite position
17 formed a large fringe on tho outside (see photograp 7
of the stem.
of test C, fig. 19), i. e., near to the glass cover, was ro tated lSOo. The next morning the ice frill e was found to
the stem, showing that proximity to the glass cover did not char!ge the location of the frm e upon the stem.
evidently determined by the ease with which the moisture can be supplied from within the plant. An examination of the cross sectioiis of plant stenis showed that sa - tubes may be located very close to the outer wall of t i! e stem. One would expect this to be the stnrting point and the most prolific source of production of tho largest fringes. In the laboratory test sample the stem showing this propert was one from which the bark had been scraped, anc?the abrasion may have been deeper on the side which produced the most ice. lant (stem without bark 2.5 mm. in diameter), situatc c r on a steep bank- was observed all winter long. Throughout this time it formed the ice fringe 011 one side. It was split as
shown by the dotted lines in figure 40, but an ice was observed in the rift. Sometinies the base of the ice tooth was almost solid and ernbraced half of the stem, as shown in figure 4B. After a rain when the ground was quite wet, the ice fringe esteded 2 to 2.5 cm. up the stem and out alorg a branch (observation of Jan. 111, as shown in figure 46. On other nioriiii-gs whe!i the ground
WRS dry and powdery, there was but 1itt)le ice formed above the loose earth which continued slidirg down the steep bare hillside. The ice friilge, however, whether a wide ribbon or a short wedge-shaped tooth (fig. 40),
half buried in the dry shiftii? soil, was always formed on the same side of the stem. #he clump of 3 or 4 plants, of which this was one stem, never formed such long ribbons as were to be observed on other stems situated on a lower level on this same bank, where the pound was always moist. The plants of test 2. describecl elsewhere, were located on the lower level of this steep hill; also stumps of &nib, from which the tops had been cut. No ice was observed to form on the cross section of the stump; but long curled ribbons of ice continued to form along that side of the stem that was at the level of the ground. The soil itself formed escclleiit samples of ground ice.l It was therefore an inturesting sight to
rise more than 1.5 cm. above t % e ground. There is evi-
have Formed on the LLinside, i. e., on % t e same side of
The location and the amount o P the ice formation is
For esample, one stem which on Febru
In the field one strong, weather-beaten
*The term I ound iee hem used by tho author must be assiimed to refer to Ice
COlUmaS Pmp& SO CSlled-EDITOtr.
ass MONTHLY WEATHER REVIEW. AUGUST, 1914
sometimes observe the ice fringes from the stumps of &n& protrudin out over the ground ice. The ground
contained a certain amount of moisture. ice formed only a 7 ter rain when the ground was wet, i. e.,
DeskpSon of photopphe of ice fringe&
The attem ts a t photographi the ice fringes as they
was owing to the fact that a t 8 a. m. the illumination was weak. A wide stop was used in the camera, and conse- uently the 3bects are in focus only in the center of the hotograph. +he serve the purpose, however, to illus-
The ice fringes are viewed at an angle of almost 45O. However, a gcneral idea of the size of the fringes niay be obtained by coni ar them with the accompanying
The photograph forming fi we 13 waa obtained on
occurred in t R e woods were far T rom satisfactory. This
trste then genera s appearance as found in the woods.
pocketknife, whic I ?? is a out 14 cni. in length.
January 7, 1914. It is typica K of what one finds as r e
f !g e in the lower left- 1 and corner is compose T- of three The
shown by the roun c f dark spot in the center. The bright-
was formed (the stalk with the three f ranches) shows t % e
ards size and general a pearance of the ice fr
whorls; the open s ace in the fringe nearest the knife is
est ice fringe in the stalk u1 the center of the picture is not unlike the large sample shown in %ures 15 and 16. This photograph shows sevea stalks with ice fringes. One formation 1 ~. the lower right-hand corner of the photo- graph is broken. The finiEa stalk u on which this frin e
bark pushed out at the base of the stem, with some ice still a-aering to it. Figure 1.1: was obtained in the middle of Januarv. The ice fzrmation in the ceater of the photograph contains four beautifully folded fringes whose markings are un- fortunately lost in the rint.
obtained by collecting a nuniber of ice fr es one cold
ed lent is due Mr. E. D. Tillyer for his painst.aking care in m g n g these photo a hs, which no doubt are the finest records yet obtaine 8P o these beautiful ice formations. e 15 the four most conspicuous ice fringes are
lettere In a, 6 , e, d, which makes identification easy in flg-
ures 16, 17, and 18. In these lates the ice fringes were
ge noticed that the stem is free from bark. e 16a an extremely thin delicate fringe may be notice 8 protruding from what appears to be a rift in the steni, but what in reality is a piece of bark. It is an excel- lent illustration of the second stage in the formation of the ice fringe as described on page 494 and illustrated in figure 3B. Figures 17 and 1Sa give further views of this ice formation. It consists of two large fringes, twisted and whorled. Figure 17a shows to advantage the oft-aientioned, thin, wed e-sha ed fringe (see fig. 16e
above the large frmges. The Cunila stalk a, shown in these hotographs, is typical of whatf one finds after
bark. The stein is 2.2 mm. in diameter and i t 1s not rifted. As shown in figure 17a, the width of the fringe adhering to the stem is 3 cm. It extends out horizontally
3 cm. from the stcm. The distance from the stem to the
extreme distal end of the loop is 1 cm. Figure 156 consists of three splinters united at the base of the stem. They are, of course, the remnants of the
The k e s t photograp !h s (figs. 15, 16, 17,. and 18) were
frost morning (Jan. 6, 191.1) and having a t em hoto- grap i ed a t the Bureau of Standards. Grateful acLowl-
hotopaphed from different si B es. In figure 15a i t may
In fi
and f), protruding (upwar d R in t e photograph) from
severa P ice formations when the stem is well stripped of
stalk, which had long since disappeared. The dark line in the wood is the pith, which is shown to better advm-
tage in figure 186 and figure 6. Figures 16 and 17 show the ith side of another splinter. We thus have a hoto-
rifted stalk and the rifted stalk (figs. 15, 16, 17, and 1Sc)
and UPOR the bare splinters. This is rn unusually iuter- esting ice formation. The peculiar whorl in the center (figs. I6 and 176 a& top views) is the meeting point of two frmges (see fig. 6>, both of which began cmving clock-
wise. The extreme thinness and the great trans arency is to be noticed (see also fig. 3d) by the light and t 1 e dark streaks through the fringes. The small ice fringes on the stalk shown in 6gures 15,
16, 17, and 1Sc are of interest because they occur upon
a thin stem which is split into two parts, the rift being
easily distiiygiished in the photographs. In fact, most of the rift is above
ice formation is also conspicuous in hav- ing ushed out some of tEe bark as illus- trated in figure 15c. This is an axcellent photographic record showiii that the ice
the ith (fig. 156Yor in &e rift of the
Ounila stem. Figurea 15,16,17, and 18d give & fur- FIo.B.-Dlagramillustrat the structure ole whorl due to the mestingof tw%ngw such spshown at B ther illustration of the formation of ice
fringes upon fragments of stems of the Cunih. The gam- le is a very small one. The stump of the stalk had to {e cut out of the ground in order to obtain the fril-ges.
Some of the soil is still adhering to the stem. One of the frii7ges is broken off. The extremely thin translucent fringe (it ap ears to be dark owirg to the dark back- ground) on t e right hand side of fi ures 15 and 1Sd is an
of the ice fringe as described on a previous pRge. The growth of the fringe is along a straight edge, which appears
almost horizontal in the photograph. This, however, is part1 owing to the peculiar curvature of the fringe. The dista 9 edge is strai ht and smooth just as it started when near the stem. Tfe photographic record is, therefore, an escellent contradiction of the hoarfrost theory of accu- mulation. In the tejts with the asphaltum (p. 493) the ice fringe had a similarly formed straight edge. The dark streak along the fragment of stem is pith. The ice fringe is upon the woody side of the stem. Figure 1s (omitted) shows the upper parts of the stem, a few loaves, aiid the showy seed capsules. All the photo- a hs show fragments of ice fringes with bright and %rE streaks due to the difference in thickness aiid bend in transparency of the ice. Fi re 19 is a hotographic record of laboratory test C. c w a s taken \ y the writer February lS, 1914. The test tube was about 20 mm. in dinmeter, which gives one some idea of the dimensions. The test is described on page494. Thisrecord is of interest main1 in showing
for some months, form ice fringes just as they do when attached to the roots.
grap $l ic record of the ice formation upon both t f e un-
the ice frir ges. This PI 7.9.
is not f ormed u on
in the photographs, ngures 16 and 17.
escellent photographic record of t a e manner of growth
that the Chn& stems, after having been in t z e laboratory
M. W. R. August 1914. To face p. 498.
FIQ. 12.-Cross section of stem of &nib matirPna. Yagdflcation 60.
PIG. 13.-Photograph of a typical field appearance of ice fringes, .--.I January 7,1914, lookmg down at an angle of about 45O.
FIG. 14.-Photograph of four t..udfully folded fringes, January, 1914.
To face p. 498. M. W. R., August, 1914.
t.
FIG. 15.-Details of ice fringes collected January 6, 1914. a, b, c, and d are identical in figures 15,16,17, and 18. (Photogmph by E. D. Tillyer, U. S. Bureau of Standards.)
-
FIG. 16.-Further details of the views in flgnre 15.
J
To face p. 499. M. W. R., August 141A
c
Fr~.-l7.-Enlarged view of the details of figure 15.
Fro. 18.-Reaults of laboratory test C, taken on February 18,1914. Test tube about 20 mm. diameter.
A U G ~T , 1914. MONTHLY ?TEATEER REVIEW. 499
Ice formution in a hrge body of water.-In view of the possibility that the ice formed at the bottom of a river (the anchor ice proper, as mentioned a t the beginning of this paper) may be owing in part to some other cause in addition to the high emissivity of the Vver bottom, it is
desirable to call attention to the following eculiar forma-
body of still water. In test D, already described, the hceptacle containing the water was a widemouth bottle, 6 cm. in diameter a t the top, and about 14 cm. in height. The bottle ed in hair felt
was therefore
tion of ice as the result of cooling and re P rigeration in a
packed in a
FIG. 7.-Test D yjth wide-Fouthed bottle, showing rurtnlns of ice suspended In the water and saw- toothed blades extendhi far down into the water.
mainly by &nduction and radiation from the top. On one occasion it was ob- served that instead of the ice freezing solid across the top, there were several ex- tremely thin curtains of ice suspended in the water as shown in -re 7. They were visible only in intense sunlight. Several thin, nar- row, saw-toothed blades ex- tended far down inside the bottle. They seemed to take the line along which refriger- ation occurred as a result of cooling, principally by con- duction and radiation a t the top of the vessel. It would be desirable to determine whether the density of these fine ice spicules is t.he same as that of a large mass of ice.
StTMMARY.
This paper deals with the formation of ice fringes upon the Dittany, Guniira niniian,a. The data here presented are based upon esperiments and observations in the field and in the laborato .
the temperature falls to freezing; but they are not a func- tion of the hoarfrost which may be present upon the ground. The ice fringes do not form upon the side of a splinter which contains the ith or upon the line of fracture, but
frin e, however, is not a function of the surface condkion
but usually no ice protrudes rom the rifts. The growth of the ice fringe ceases when the ground is frozen to a de th of 2 to 3 cm., and when the moisture
It was observed t ? at the ice fringes are formed when
upon the outer woo 1 y surface. The formation of the ice
f
of t a e stem. The stem is fre uently found to be cracked,
in the stem is f rozen.
result of hydrostatic pressure exerted by the roots, which are erennial. A E the observations agree in showing that the moisture
rises in the steni as the result of capillary attraction. The height (1 to 5 cm.) to which the moisture can rise within
the stem is overned partly by the rate of evaporation from the su 3 ace.
which show the st,ructure of stem of plants which c o no; form ice fringes; also photomicrogr~ph of sections of stems of plants which forni ice fringcs. It is shown that those plants which form ice fringes the most readily and in the greatest abundance hnve the most snp tubes. The ice fringe is a coniFositc of a number of ver thin
fringe was observed from its T -e y beghiniiig. The fist, stnge in the production of the icc fringe consists of a
single row of fine hnirlilie filaments of ice. This row of ice filmients lengthens up find down the stem. The iilnments increase 111 nunih~r, thus foniiillg a solid wcdge-
sha ed tooth of ice, which constit.utcs the second sta e
wed e-shaped tooth of icc widens and increases in length,
soak out of the stem. There appears to be no difference between the forma- tion of these ice fringes and the ground ice fornied on wet soils other than that in the latter a particle of gravel usuiilly forms the nucleus to start 6lie congelation. In both cases the moisture is brought t,o the surface by capillary action. When the rate of supply to the surface is more rapid than the loss by evaporation, and the air is at a sufficiently low temperature, ice is fornied.
REFERENCES.
Photomicrographs of thin scct.ions of plants are
ribbons. In the laboratory the fonn:ition of t r le ice
of c r evelopment. In the third st:igcr of development t K e
as t a 8 result of freezing of the water which continues to
(1) Abbe, Cleveland. Ice columns in gravelly mil. Am. metl. jour., Roston, April, 1SO3. 9: 523-525. Also in Monthly weath. rev., Washington, A ril, 1905, 33: 157-16s. (2) Barnes, goward T. Ice fr,rmat;on with special reference to anchor ice and frazil. Monthly Weather Review, Washington, May,
1907, 36: 225. (3) Herschel, Sir John. I n Phil. mag., Londm, 1533, (3) 2: 110. (4) Elliot, Stephen. Sketch of the botany of South Carolina and Georgia, 1S34, v. 2, p. 323. Quotcd by Le Conte. (5) Le Conte, John. Jra Roc. Amer. B R ~~C . adv. wi., 1S50, 8: 20. (6) Ward, Lester. Frost freaks of the Dittany. Butan. pz., 1893, 18: 153. (7) Ward uotes Grays Manual of 1S4G, in which Helianthemum
cumdense is (aescribed as behaving in a similar way.
-., . , /.
ARE LIGHTNINQ FLASHFS UNIDIRECTIONAL OR
OSCILLATING ELECTRIC DISCEARGESP
By CHARLES F. MARVIN, Chief.
[Dated Weather Bureau, Washington, D. C., June 13,1914.1
L. A. De Blois, in making experiments upon electrical dischar es in a wireless aerial (natural period 400,000)
caused % y neighboring lightning flashes, using for this purpose both a static voltmeter and an oscillograph whose behavior was photographed or esaniined by means of a revolving mirror, found only oearly instantaneous laterrrl flicks of the oscillograph needle. In some cases the needle showed a number of niinor oscillations. exe- cuted during the return of the needle to its zero position. The duration of a discharge of this ldnd was a t least 0.0034 second. The periodic time of the oscillograph was 5,000
to 6,000 per second. De Blois states that-
In no recorda was there any indication of regular eriodio high-fre-
quency oscillations in the iuduced current. Had %ey existed, the
1 This paper and the following comment refers to the prellminary edition of the p p e c by L. A. De Blols Some invsstlgations on lightning rootectiun for buildinas,  pre- sented at 2grlth &thg Am. Instit. Elect. Eng., Washkgton, Aim. 24-25, 19!4, and appear IU Trans. Am. Instit. Elect. Eng., 1914, %3:563-579, and pL 25. Tho Illustra- trans oi%t paper am not reprod& a -~m m B .