729 



WATER. 



WATER. 



739 



then with a rigid adhesion. When five or six pieces are grouped in a 

 contorted shape, as an S, and one end piece be moved carefully, all will 

 move with it rigidly ; or, if the force be enough to break through the 

 joint, the rupture will be with a crackling noise, but the pieces will 

 still adhere, and in an instant become rigid again. As the adhesion is 

 only by points, the force applied should not be either too powerful or 

 in the manner of a blow. I find a piece of paper, a small feather, or a 

 camel-hair brush applied under the water very convenient for the 

 purpose. When the point of a floating wedged shaped piece of ice is 

 brought under water against the corner or side of another floating 

 piece, it sticks to it like a leech ; if, after a moment, a paper edge be 

 brought down upon the place, a very sensible resistance to the rupture 

 at that place is felt. If the ice be replaced by like rounded pieces of 

 wood or glass, touching under water, nothing of this kind occurs, nor 

 any signs of an effect that could by possibility be referred to capillary 

 action ; and finally, if two floating pieces of ice have separating forces 

 attached to them, as by threads connecting them and two light 

 pendulums, pulled more or less in opposite directions, then it will be 

 seen with what power the ice is held together at the place of regelation 

 when the contact there is either in the flexible or rigid condition, by 

 the velocity and force with which the two pieces will separate when 

 the adhesion is properly and entirely overcome." 



In Dr. Faraday's second published notice of regelation (' Exp. Res. 

 in Chem. and Phys.,' pp. 380, 381), he had adduced the growth of 

 crystals of camphor and of iodide of cyanogen, by the deposition of 

 solid matter upon them from an atmosphere unable to deposit like 

 solid matter upon the surrounding glass, except at a lower tempera- 

 ture ; and that of crystals in a solution, by the deposition of solid 

 matter upon them which is not deposited elsewhere in the solution, to 

 illustrate the extension of the principle of action which is manifested 

 in regelation. In his reasoning on the nature of that principle, he also 

 rested on the fact, that ice has the same property as camphor, sulphur, 

 phosphorus, metals, &c., which cause the deposition of solid particles 

 upon them from the surrounding fluid, that would not have been so 

 deposited without the presence of the previous solid portions. 



But the further experimental inquiry to which he has now sub- 

 jected the phenomena of regelation, appears to have conducted him to 

 a view of them which is not altogether reconcileable with his previous 

 inferences respecting the extension of the principle. He now asks, 

 " Is this remarkable property peculiar to water, or is it general to all 

 bodies ? In respect of water, it certainly seems to offer us a glimpse 

 into the joint physical action of many particles, and into the nature of 

 cohesion in that body when it is changing between the solid and liquid 

 state. I made some experiments on this point ; " which he proceeds 

 to relate. 



The metals bismuth, tin, and lead did not present the slightest trace 

 of an action corresponding to regelation. Melted nitre appeared at 

 times to lihow traces of the power ; but, on the whole, Dr. Faraday is 

 inclined to think that the effects observed resulted from the circum- 

 stance that the solid rods experimented with had not acquired through- 

 out the freezing temperature. Nitre, however, he remarks, " is a body 

 which, like water, expands in solidifying ; and it may possess a certain 

 degree of this peculiar power." Glacial acetic acid, he finds, is not 

 merely without regelating force, but actually presents a contrast to it. 



" Many results were tried (without much or any expectation), crys- 

 tals of them being brought to bear against each other by torsion force, 

 in their saturated solutions at common temperatures. In this way the 

 following bodies were experimented with : Nitrates of lead, potassa, 

 soda ; sulphates of soda, magnesia, copper, zinc ; alum ; borax ; chlo- 

 ride of ammonium ; ferro-prussiate of potassa ; carbonate of soda ; 

 acetate of lead ; and tartrate of potassa and soda ; but the results were 

 all negative." , 



Dr. Faraday's " pre.-ent conclusion, therefore, is that the property ' 

 of regelation " is special for water, and that the view " he has " taken 

 nf its physical cause" "that a particle of water, which could retain 

 the liquid state whilst touching ice only on one side, could not 

 retain the liquid state if it were touched by ice on both sides, but 

 became solid, the general temperature remaining the game" "does 

 not appear to be less likely now than at the beginning of this short 

 investigation, and therefore has not sunk in value among the three 

 explanations given," namely, his own and those of Professor James 

 Thomson and Principal Forbes, respectively, which have been stated in 

 our former account of this subject. 



In the ' Proceedings of the Royal Society ' for May 2, 1861 (vol. xi., 

 'S-204), appears a note by Professor James Thomson, in which 

 he states that he still adheres to the explanation of Principal Forbes's 

 experiment, cited from a former paper by him in our article ICE, as 

 mainly correct, though admitting of modification in reference to a 

 point which seems to him to be as yet rather obscure : " the influence, 

 namely of the tension in the ice due to its own weight, which makes 

 it wit bo subject internally to simply atmospheric pressure." Professor 

 Thomson also points out some additional conditions, almost necessarily 

 present in the experiment, which, under his view of the plasticity of 

 ice, would act in conjunction with those originally adduced, and would 

 increase the rapidity of the union. But his principal object in this 

 comer it from the interpretation given by Pro- 



fessor Faraday of his recent expel imcntH, as above, and to express 

 the opinion that they are in perfect accordance with, nnd t : \ 1 to con. 



firm, his own theory, and its application to the various observed cases 

 of the union of two pieces of moist ice when placed in contact. This 

 he does, after describing Faraday's results, in these terms : " My 

 view of the phenomena of these experiments is as follows : the first 

 contact of the two pieces of ice cauuot occur without impact, and con- 

 sequent pressure ; and, small as the total force may be, its intensity 

 must be great, as the surface of contact must be little more than a 

 geometrical point. This pressure produces union by the process of 

 melting and regelation described by me in previous papers. On the 

 application of the forces from the two feathers, at one side of the point 

 of contact, tending to cause separation, the isthmus of ice formed by 

 the union of the two pieces, comes to act as a tie or fulcrum subject to 

 tensile force ; and, consequently, a corresponding pressure will occur 

 at the side of the isthmus far from the feathers, and that pressure will 

 effect the union of the ice at the side where it occurs. The tensile 

 force, it may be readily supposed, tends to preserve the isthmus, inter- 

 nally at least, in the state of ice, whatever may be its influence on the 

 external molecules of the isthmus, and to solidify such water as, having 

 occupied pores in the interior during previous compression, may now, 

 by the linear tension or pull, be reduced in cubical pressure or hydro 

 static pressure, because the melting-point of wet ice is raised by dimi- 

 nution of pressure of the water in contact with it. The pull applied 

 to the isthmus thus appears to put it out of the condition in which my 

 theory has clearly indicated a cause of plasticity, and, I presume, makes 

 it cease, or almost entirely cease, to be plastic. I believe no plastic 

 yielding of ice to tension has been discovered by observation in any 

 case, and I think there are theoretical reasons why ice should be 

 expected to be very brittle in respect to tensile forces. The isthmus 

 then being supposed devoid of plasticity at its extended side, ultimately 

 breaks at that side when the opening motion caused by the feathers 

 has arrived at a sufficient amount to cause fracture; and the ice 

 newly formed on the compressed side comes now to act as a tie, instead 

 of the part which has undergone disruption, and holds together the 

 two pieces of ice, or serves as a fulcrum under tension to communicate 

 a compressive force to the points of the two pieces of ice immediately 

 beyond it ; and so the rolling action with a constant union at the point 

 of contact goes forward. It is to be observed, that the leverage of the 

 forces applied by the feathers is so great, compared with the distance 

 from the fulcrum or tensile part of the isthmus, to the compressed 

 part in process of formation at the other side as that the compression 

 may usually be considered almost equal to the tension ; and the tension 

 in the extended part cannot be of small intensity, being sufficient to 

 break that side of the isthmus. In the experiments which gave flexible 

 adhesion seemingly under tension, it is not to be admitted that tension 

 was really the condition under wluch the ice existed at the places 

 where the union was occurring. To apply a simple disruptive force to 

 the whole isthmus of ice, it would be necessary to take very special 

 precautions in order to arrange that the line of application of the dis- 

 ruptive forces should pass through the point of contact of the two 

 pieces. If that were done, and the forces were gradually increased till 

 the cohesive strength of the isthmus were overcome, it is clear that the 

 two pieces of ice would separate altogether, and there would be no 

 flexible adhesion ; but the flexible adhesion, when it occurs, is essen- 

 tially dependent on the existence of an intense pressure at the side of 

 the isthmus remote from the line of the externally applied disruptive 

 forces, or of the single force applied in some of the experiments to one 

 only of the pieces, and resisted by the inertia of the other." 



While Dr. Faraday was engaged in the experimental corroboration of 

 the cause to which he had originally as-igned regelation, and in the 

 limitation of the inferential views of its extension which he had first 

 taken, a less conspicuous inquirer had been led to found upon those 

 views and upon a known fact in the physical history of glass, a theory 

 of the universality of regelatiou. This had been indicated, and the 

 fact in question stated, at the end of our former account of the subject 

 in the article ICE. In the ' Proceedings of the Royal Society ' (vol. x., 

 pp. 450-460), Dr. Faraday's ' Note on Regelation ' is followed by Mr. 

 Brayley's ' Notes on the Apparent Universality of a Principle analogous 

 to Regelation ; on the Physical Nature of Glass ; and on the Proba- 

 bility of the Existence of Water in a state analogous to that of Glass.'* 

 In the first of the three ' Notes ' of which Mr. Brayley's paper consists, 

 the view of the subject taken in ICE (col. 817) is resumed in greater 

 detail, the facts there mentioned being regarded as " indicating tho 

 existence of a condition of matter which may bo termed arrested 

 liquidity, but yet is not, in the most perfect sense, solidity." It is 

 assumed also to be highly probable that the process by which two 

 plates of polished plate-glass become one is, in reality, analogous to 

 that of regelation in ice, and finally dependent on the same principles, 

 whatever their true character may be conceived or shall ultimately be 

 determined to be. Facts are stated, from which it is inferred that tho 

 state of the interior portions of a plate of plate-glass is similar to that 

 of glass in general at certain temperatures much below its fusing point, 

 when it presents such remarkable cliaractcrs of plasticity, tenacity, and 

 ductility. These facts are stated to recall the view taken by Person, 

 and adopted by Principal Forbes [Ion, col. 816 ; THAW], of the sinii- 



* Three notes wcro received by, and rcail to, the Royal Society on the 2Cth of 

 April, 1SOO, alter Dr. Faraday had given nu oral account, experimentally 

 lUiutrnlcu, of tho contents of Lis owa ' Note,' which had bceu received in tho 

 preceding month. 



