7J7 



WATER. 



WATER. 



718 



will inclose fur a i.i..v capillary jianrtt, and thus the above 

 account* satisfactorily for the known utructure of glacier ice. 1'rofeanor 

 Tjrodall made an experiment on this point in which, by a gradually 

 increaalng prMture, be produced in ice fissure* of thU description 

 accurately resembling those made evident by the infiltration experi- 

 ment* of SI. Agassis in the glacier of the Air. 



Since the publication of Dr. Tyndall'i researches, and that of the 

 paper* by Principal (late Professor) James D. Forbes and Professor 

 James Thornton, the contents of which were stated in the former article, 

 1 >r Faraday has entered into a new experimental investigation of it, 

 which has appeared in the ' Proceedings ' of the Royal Society, vol. x. 

 p. 440-450, under the title of ' Note on Kegelation,' in which he has 

 ikUo more fully described that property than in his previous papers. 

 Of the new facto he has observed, and of the conclusion* he has founded 

 upon them, the following are the moat important. 



' Two p.eces of thawing ice if put together adhere and become one; 

 at a place where liquefaction was proceeding congelation suddenly 

 occurs. The effect will take place in air, in water, or in vacuo. It 

 will occur at every point where the two pieces of ice touch, but not 

 with ice below the freezing point, that is, with dry ice, or ice BO cold 

 as to be everywhere in the solid state." 



" Though some might think," Dr. Faraday resumes, " that Professor 

 [J.] Thomson, in his last communication [IcE, col. 816], was trusting 

 to changes of pressure and temperature so inappreciably small as to be 

 not merely imperceptible, but also ineffectual, still he carried his con- 

 ditions with him into all the cases he referred to, even though some of 

 his assumed pressures were due to capillary attraction, or to the con- 

 sequent pressure of the atmosphere only." 



In order to exclude all pressure of thu particles of ice on each other 

 due to capillary attraction or the atmosphere, Dr. Faraday prepared to 

 experiment altogether under water, arranging a bath of that fluid, 

 maintained at 32' Fahr., which by the method he employed it could 

 be for a week or more. [THAW.] 



Two similar blocks of good Wenham-lake ice were placed in the 

 water with their opposed faces about two inches apart, each being 

 moored to a particular place by woollen thread attached to pieces of 

 lead, so that they were sunk entirely under the surface of the ice-cold 

 water. If brought near to each other and then left unrestrained , they 

 separated, returning to their first position with considerable force. If 

 brought into the slightest contact, regelation ensued, the blocks ad- 

 hered, and remained adherent, notwithstanding the force tending to 

 pull them npart. They would continue thus, even for twenty-four 

 hours or more, until they were purposely separated, and would appear 

 (by many trials) to have the adhesion increased at the points where 

 they first touched, though at other points of the contiguous surfaces a 

 feeble thawing action went on, causing a dissection of the ice, develop- 

 ing its mechanical composition, and showing it to consist of layers of 

 greater and less fusibility, horizontally disposed in the ice whilst in the 

 act of formation. " In this case, except for the first moment, and in a 

 very minute degree, there was no pressure, either from capillary action 

 or any other cause. On the contrary, a tensile force of considerable 

 amount was tending all the time to separate the pieces of ice at their 

 points of adhesion ;" where still the adhesion went on increasing. 

 Arrangements were next made to ascertain whether anything like 

 soft adhesion occurred, such as would allow slow change of position 

 without separation during the action of the tensile force.- It was 

 fi-iiud that not the slightest motion of the blocks in relation to each 

 other took place in the thirty-six hours during which the experiment 

 was continued. " This result, as far as it goes, is against the necessity 

 of pressure to regulation, or the existence of any condition like that of 

 softness or a shifting contact." 



Torsion force was then employed as an antagonist to regelation. The 

 ice-blocks being separate, were adjusted in the water so as to be 

 parallel to each other, and about 1 4 inch apart. If made to approach 

 each other on one side, by revolution in opposite directions on vertical 

 axes, a piece of paper being between to prevent ice-contact, the torsion 

 force set up caused them to separate when left to themselves ; but if 

 the paper were away, and the ice pieces were brought into contact, by 

 however alight a force, they became one, forming a rigid piece of ice, 

 though the strength was, of course, very small, the point of adhesion 

 and solidification being simply the contact of two convex surfaces of 

 small radius. It was found, also, that there was no more tendency to 

 a changing shape than in the case before examined. If the separating 

 force weir increased, but unequally, as respects the two pieces, then 

 the congelation at the point of contact would give way, and the pieces 

 of ice would move in relation to each other. Yet they would not 

 separate, though the torsion force employed was constantly tending to 

 separate them. If a slip of wood, applied to change the mutual 

 position of the two pieces of ice without separating them, were re- 

 tained for a second undisturbed, then the two pieces of ice became 

 tiled rigidly to each other in their new position, and maintained it 

 when the wood was removed, but under a state of restraint ; and when 

 sufficient force was applied, by a slight tap of the wood on the ice to 

 break up the rigidity, the two pieces of ice would re-arrange themselves 

 under the torsion force of their respective threads, yet remain united ; 

 and, assuming a new position, would in a second or less again become 

 rigid, and remain inflexibly conjoined as before. By managing the 

 continuous motion of one piece of ice, it could be kept associated with 



the other by a tlexiMc ]>oint of attachment for any length of 

 could be placed in various angular positions to it, could be un 

 retaining it quiescent for a moment) to assume and hold permanently 

 any of these positions when the external force was removed, could be 

 changed from that position into a new one, and, within certain limit*, 

 could be made to possess at pleasure and for any length of time 

 a flexible or a rigid attachment to its associated block of i< 

 observing these states, convex surfaces of contact are necessary, so that 

 the contact may be only at one point. If there be several places of 

 contact, apparent rigidity is given to the united mass, though each of 

 the places of contact might be in a flexible, and, so to say, adhesive 

 condition. " It is not at all difficult to arrange a convex surface, so 

 that, bearing at two places only on the sides of a depression, it should 

 form a flexible joint in one direction, and a rigid attachment in a 

 direction transverse to the former." 



The following are Dr. Faraday's inductions from these results, 

 which cannot be abridged : " So regelation includes a flexible acli 

 of the particles of ice, and also a rigid adhesion. The Iran 

 between these two states takes place when there is no external force 

 like pressure tending to bring the particles of ice together, but, on the 

 contrary, a force of torsion is tending to separate them ; and, if respect 

 be had to the mere point of contact on the two rounded surfaces where 

 the flexible adhesion is exercised, the force which tends to separate 

 them may be esteemed very great. The act of regulation cannot be 

 considered as complete until the junction has become rigid, and there- 

 fore I think that the necessity of pressure for it is altogether excluded. 

 No external pressure con remain (under the circumstances) after the 

 first rigid contact is broken. All .the forces which remain tend to 

 separate the pieces of ice ; yet the first flexible adhesions and all the 

 successive rigid adhesions which ore made to occur are as much the 

 effects of regelation as those which occur under the greatest pressure." 



" The phenomenon of flexible adhesion under tension look - 

 much like sticking and tenacity; and 1 think it probable that Professor 

 Forbes will see in it evidence of the truth of his view. I cannot, 

 however, consider the facts as bearing such an interpretation ; because 

 I think it impossible to keep a mixture of snow and water for hours 

 and days together without the temperature of the mixed mass becoming 

 uniform ; which uniformity would be fatal to the explanation. My 

 idea of the flexible and rigid adhesion is this : Two convex surfaces 

 of ice come together ; the particles of water nearest to the place of 

 contact, and therefore within the efficient sphere of action of those 

 particles of ice which are on both sides of them, solidify ; if the con- 

 dition of things be left for a moment, that the heat evolved I 

 solidification may be conducted away and dispersed, more particles 

 will solidify, and ultimately enough to form a fixed and rigid junction, 

 which will remain until a force sufficiently great to break through it 

 is applied. But if the direction of the force resorted to can be relieved 

 by any hinge-like motion at the point of contact, then I think that the 

 union is broken up among the particles on the opening side of the 

 angle, whilst the particles on the closing side come within the effectual 

 regelation distance; regelation ensues there, and the adhesion is 

 maintained, though in an apparently flexible state. The flexibility 

 appears to me to be due to a series of ruptures on one side of the centre 

 of contact, and of adhesion on the other, the regelation, which is 

 dependent on the vicinity of the ice surfaces, being transferred as the 

 place of efficient vicinity is changed. That the substance we are con- 

 sidering is as brittle as ice, does not make any difficulty to mo in 

 respect of the flexible adhesion ; for if we suppose that the poiut of 

 contact exists only at one particle, still the angular motion at that 

 point must bring a second particle into contact (to suffer i- liiion) 

 before separation could occur at the first ; or if, as seems proved by 

 the supervention of the rigid adhesion upon the flexible state, many 

 particles are concerned at once, it is not possible that all these should 

 be broken through by a force applied on one side of the place of 

 adhesion, before particles on the opposite side should have an oppor- 

 tunity of regelation, and so of continuing the adhesion." 



The changes of temperature and pressure in the process of regela- 

 tion, as here investigated, Dr. Faraday thinks, are too infinitesimal to 

 go for anything ; and in illustration of this opinion, ho describes an 

 experiment. For this, however, as well as for the manipulation of 

 the experiments in general, we must refer to his paper ; but an 

 addendum to it we now cite, as it details on easy method of examining 

 the various phenomena of regelation which Lave been ascertained. 

 " Take a rather large dish of water at common temperatures. Preparo 

 some flat cakes or bars of ice, from half an inch to an inch t!ii.-k, 

 remler the edges round, and the upper surface of each pii-ee convex, by 

 holding it against the inside of a warm saucepan cover, or in any other 

 way. When two of these pieces are put into the water they wi;l 

 having perfect freedom of motion, and yet only the centr.il part of the 

 upper surface will be above the fluid, when, therefore, the pieces 

 touch at their edges, the width of the water-surface above the place of 

 contact may be two, three, or four inches, and thus the effect of 

 capillary action be entirely removed. By placing a plate of clean dry 

 wax or spermaceti upon the top of a plate of ice, the latter may be 

 entirely submerged, and the tendency to approxim at ion from capillary 

 action into a force of separation. \\ hen two or u. 



such floating pieces of ice are brought togeth. i by eoi.t.. t at some point 

 under thu wau.r, they adhere ; first with an apparently flexible, and 



