156 



visibly and tangibly viscid. We even know that water may be cooled 

 much below the ordinary freezing-point and yet remain fluid. 



Professor Forbes regards Mr. Faraday's fact of regelation as being 

 one which receives its proper explanation through his theory described 

 above ; and, in confirmation of the supposition that ice has a tendency 

 to solidify a film of water in contact with it, and in opposition to the 

 theory given by me, that the regelation is a consequence of the low- 

 ering of the melting-point in parts pressed together, he adduces an 

 experiment made by himself, which I admit presents a strong appear- 

 ance of proving the influence of the ice in solidifying the water, to be 

 not essentially dependent on pressure. This experiment, however, I 

 propose to discuss and explain in the concluding part of the present 

 paper. 



Professor Forbes accepts my theory of the plasticity of ice as being 

 so far correct that it points to some of the causes which may reason- 

 ably be considered, under peculiar circumstances, to impart to a 

 glacier a portion of its plasticity. In the rapid alternations of pres- 

 sure which take place in the moulding of ice under the Bramah's press, 

 it cannot, he thinks, be doubted that the opinions of myself and my 

 brother Professor Wm. Thomson are verified*. 



Mr. Faraday, in his recently published ' Researches in Chemistry 

 and Physics/ still adheres to his original mode of accounting for the 

 phenomenon he had observed, and for which he now adopts the name 

 "regelation;" or, at least, while alluding to the views of Prof. 

 Forbes as possibly being admissible as correct, and to the explanation 

 offered by myself as being probably true in principle, and possibly 

 having a correct bearing on the phenomena of regelation, he consi- 

 ders 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 possessing cohesion, i. e. being either in the liquid 

 or the solid 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 de- 

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



* Forbes ' On the Recent Progress and Present Aspect of the Theory of Glaciers,' 

 p. 12 (being Introduction to a volume of Occasional Papers on the Theory of 

 Glaciers), February 1859. 



