ill 



1. 1- 



round the poinU of cunUct leave* the piece* united by slender 

 column* of the suUtance." Phil. Trans.,' 1857, p. 339. 



Mr. Faraday, in hi* more recently published ' Experimental Re- 

 searches in Chemistry and Physic* ' (being essentially ^publication 

 in a collective form of hi* paper* on subject* belonging to those 

 *oiooe, flnt publuhad in the ' Philosophical Tnuiaaction*,' and in 

 MTeral scientific journal*), adhere* to hi* original mode of accounting 

 for the phenomenon he had obaarred, adopting the name Regelation, 

 applied to it by Protector TyndalL While alluding to certain view* of 

 Professor Forbes, which will presently be stated, a* possibly being 

 .vlmmuble a* correct, and to an explanation offered by Professor James 

 Thomson a* being probably true in principle, and possibly having a 

 correct bearing on the phenomena of regelation, ho considers that the 

 principle originally assumed by himself may after all be the sole cause 

 of the effect. The principle he has in view, he then states as being, 

 when more distinctly expressed, the following : " In all uniform 

 bodies, pinsBSsing cohesion, that is, being either in the liquid or the 

 olid state, particles which are surrounded by other particles having 

 the like state with themselves tend to preserve that state, even though 

 subject to variations of temperature, either of elevation or depression, 

 which if the particles were not so surrounded, would cause them 

 instantly to change their condition." Referring to water in illustra- 

 tion, he says that it may be cooled many degrees below 32 Fahr., and 

 still retain its liquid state ; yet that if a piece of the same chemical 

 substance ice, at a higher temperature, be introduced, the cold water 

 frames and becomes warm. He point* out that it is certainly not the 

 change of temperature which causes the freezing, for the ice introduced 

 is warmer than the water; and he says he assumes that it is the 

 difference in the condition of cohesion existing on the different sides of 

 the changing particles which sets* them free and causes the change. 

 Exemplifying, in another direction, the principle he is propounding, 

 he refers to the fact that water may be exalted to the temperature 

 of 270* Fahr., at the ordinary pressure of the atmosphere, and yet 

 remain water, but that the introduction of the smallest particle of 

 air or steam will cause it to explode, and at the same time to fall 

 in temperature. He further alludes to numerous other substances, 

 such as acetic acid, sulphur, phosphorus, alcohol, sulphuric acid, 

 ether, and camphine, which manifest like phenomena at their freezing 

 or boiling point* to those referred to as occurring with the sub- 

 stance of water, ice, and steam ; and he adverts to the observed 

 fact, that the contact of extraneous substances with the particles of a 

 fluid usually seta these particles free to change their state, in conse- 

 quence, he says, of the cohesion between them and the fluid being 

 imperfect ; and he instances that glass will permit water to boil in 

 contact with it at 212 Fahr., or by preparation can be made so that 

 water will remain in contact with it at 270 Fahr., without going off 

 into steam, but that an ordinary piece of glass will set the water off 

 at once to freeze. 



Professor Faraday afterwards comes to a point in his reasoning 

 which he admit* may be considered as an assumption. It is, " that 

 many particles in a given state exert a greater sum of their peculiar 

 cohesive force upon a given particle of the like substance in another 

 state than few can do; and that a* a consequence a water particle 

 with ice on one side and water on the other, is not so apt to become 

 solid a* with ice on both sides ; also that a particle of ice ' at the 

 surface of a mass [of ice] in water is not so apt to remain ice as when, 

 being within the mass, there is ice on all sides, temperature remaining 

 the same." 



" This supposition," Professor James Thomson observes, " evidently 

 contains two very distinct hypotheses. The former, which has to do 

 with ice and water present together, I certainly do regard as an 

 assumption unsupported by any of the phenomena which Mr. Faraday 

 has adduced. The other, which has to do with a particle of ice in the 

 middle of continuous ice, and which assumes that it will not so readily 

 change to water, as another particle of ice in contact with water, I 

 think is to be accepted a* probably true. I think the general bearing 

 of all the phenomena he ha* adduced, is to show that Uie particles of 

 substance when existing all in one state only, and in continuous con- 

 tact with one another, or in contact only under *pecial circumstances 

 with other substances, experience a dijfirulty of making a beginning of 

 (or change of itatc, whether from liquid to solid, or from liquid to 

 gaseous, or probably also from solid to liquid ; but I do not think 

 anything has been adduced showing a like difficulty as to their under- 

 going a change of state when the substance is present in the two states 

 already, or when a beginning of the change has already been made. 

 I think that when water and ice are present together, their freedom to 

 change their state on the slightest addition or abstraction of beat, or 

 the slightest change of pressure, is perfect I therefore cannot admit 

 the validity of Mr. Faraday's mode of accounting for the phenomena 

 of regelation.' 



The view of the subject involved in the statement of Professors 

 Faraday and Tyndall, given above (before the former had enunciated 

 his own view* in the more extended form), was adopted by the latter 

 physicist as the basis of a theory by which he proposed to explain the 

 viscosity or plasticity of ice previ.mxly known to be the quality in 

 glaciers [ GLACIERS, in NAT. HIST. Div.J, in virtue of which their 

 motion down their valleys is produced by gravitation ; but which he 

 described as being not true viscosity, but, in brief, a* the result of 



fracture, change of position of the fractured parts, and regelat . 

 those parts in their new position ; the term rcyelation being now first 

 given to the fact, the scientific importance of which had been originally 

 pointed out by Faraday.* Professor James Thomson, Queen's College, 

 Belfast, whose first express contribution to the subject we now have to 

 record, conceiving Professor Tyndall'* theory of the viscosity of glacier 

 ice to be wrong, made public a theory of his own involving a different 

 view of the nature of the phenomenon of regelation. This, a* sketched 

 in outline by himself, is as follows : If to a mass of ice at it* melting- 

 ]'im, pressures tending to change it* form be applied, there will be a 

 continual succession of pressures applied to particular part* liquefac- 

 tion occurring in those parts through the lowering of the melting- 

 point by pressure (experimentally demonstrated in 1850 by Professor 

 William Thomson, of Glasgow, his brother) evolution of the cold 

 by which the so melted portions had been held in the frozen state, 

 dispersion of the water so produced in such directions as will afford 

 relief to the pressure, and recongelation, by the cold previously 

 evolved, of the water on its being relieved from this' pressure : and the 

 cycle of operations will then begin again ; for the part* recongealed, 

 after having been melted, must in their turn, through the yielding 

 of other parts, receive pressures from the applied forces, thereby to 

 be again liquefied and to proceed through successive operations as 

 before.t 



Professor James D. Forbes adopts the view of Persor, that the disso- 

 lution of ice is a gradual, not a Hidden , process, and so far resembles the 

 tardy liquefaction of fatty bodies, or of the metals, which in melting 

 pass through intermediate stages of softness or vico.-ity. He thinks 

 that ice must essentially be colder than water in contact with it ; that 

 between the ice and the water there is a film varying in local tempe- 

 rature from side to side, which may be called plastic ice, or viscid 

 water ; and that through this film heat must be constantly passing 

 from the water to the ice, and the ice must be wasting away, though 

 the water be what is called ice-cold. On this, Professor J. Thomson 

 thus comments : " There is a manifest difficulty in conceiving the 

 possibility of the state of things here described ; and I cannot help 

 thinking that Professor Forbes has been himself in some degree sensible 

 of the difficulty ; for in a note of later date by a few months than the 

 paper itself [in which the view had been given], he amends the expres- 

 sion of his idea by a statement to the effect that, if a small quantity of 

 water be inclosed in a cavity in ice, it will undergo a gradual rtyda- 

 don[], that U. that the ice will in this case be gradually increased 

 instead of wasted." In reference to the first case, Professor J . Thomson 

 asks, " What becomes of the cold of the ice, supposing there to be no 

 communication with external objects, by which heat might be added to 

 or taken from the water and ice jointly considered ! Does it go into the 

 water and produce viscidity beyond the limit of the assumed thin film 

 of viscid water at the surface of the ice 1 Precisely a corresponding 

 question may be put relatively to the second case, that of the large 

 quantity of ice inclosing a small quantity of water, in which the 

 reverse process is assumed to occur. Next, let an intermediate case be 

 considered, that of a medium quantity of ice, and in which no heat 

 nor cold, practically speaking, is communicated to the water or the ice 

 from surrounding objects. This, it is to be observed, ia no mere theo- 

 retical case, but a perfectly feasible one. The result, evidently, if the 

 previously described theories be correct, ought to be that tin- 'in 

 of ice and water ought to pass into the state of uniform viscidity. 

 Professor Forbes' own words distinctly deny the permanence of the 

 water and ice in contact in their two separate states ; for he says, 

 ' Bodies of different temperatures cannot continue so without inter- 

 action. The water must give off heat to the ice ; but it spends it in 



The term* fracture and rtf elation. Professor J. Thornton remark*, then 

 came to be the brief expreuion of Professor TymUll's idea of the plssticitv of 

 Ice. Bat the former, whose views we re about to gire in the text, observes 

 on the nomenclature of the process, " I suppose the term resolution has been 

 (riven by Professor Tyndall as denoting the second, or mending stage in his 

 theory of 'fracture and regtlation.' Congelation would seem to me the more 

 proper word to us* after fracture, as rryelatum implies previous melting. If 

 my theory of melting e frrtntri and frnziny again by relief of prruurr be 

 admitted, then the term regelation will come to be quite suitable for a part of 

 the process of the union of the two piece* of Ice, though not for the whole, 

 which then ought to be daiignatert as the process of milling and ref elation." 

 'Proceedings of the Koyal Society* (vol. x.) for Nov. 24, 1869, p. 154, note. 

 It may be remarked on this, however, that while the latter uhrwe may be 

 tequlrcd In discussing the phenomena of glaciers, as the word re-gelation itself 

 implies that a previous froien state has existed, it would appear to be sufficient 

 In designating simply the physical process to which It was originally applied. 



t In explanation of the simplest case of regelation, Professor J. Thomson 

 expressed himself in the following manner in a communication to the British 

 Association, In 1857 : "The two pieces of in (at 32') on being pressed 

 together at the point of contact, ill, at that place, in virtue of the pressure, be 

 In part liquefied and reduced in temperature, and the cold evolved In their 

 liquefaction will cause some of the liquid film intervening between the two 

 masses to freecc." 



t Sir J. . W. Berschel, when be terms regelation " a sort of welding " 

 (UAH.), appears to concur with this view. 



($ Tnis use of the term regelation we conceive to be at once inaccurate, and 

 tending to ambiguity. The water in this case need not have been frozen before ; 

 and to call It* solidification, by the effect of the contiguous Ice, regelation, is 

 erroneously to extend the application of that term to all canes in which water, 

 however originally resulting, Is froien by the contact of ice.] 



