Prof. Tyudall on some Physical Properties of Ice. 347 



motion inconsistent with liquidity. //* other words, it becomes 

 frozen, and cements the two surfaces of ice between which it is en- 

 closed*. 



If I am right here, the importance of the physical principles 

 involved are sufficiently manifest ; if I am wrong, I hope I have 

 80 expressed myself as to render the detection of my error easy. 

 Right or wrong, my aim has been to give as explicit utterance 

 to my meaning as the subject will admit of. 



§ V. 



43. Mr. Faraday's experiments on the freezing together of 

 pieces of ice at 32° F., and all of those recounted in the paper 

 published by Mr. Huxley and myself, find their explanation in 

 the principles here laid down. The conversion of snow into neve, 

 and of neve into glacier, is perhaps the grandest illustration of 

 the same principlet- It has been, however, suggested to me 

 that the sticking together of two pieces of ice may be an act of 

 cohesion, similar to that which enables pieces of wetted glass, 

 and other similar bodies, to stick together. This is not the case. 

 There is no sliding motion possible to the ice. When contact 

 is broken, it breaks with the snap due to the rupture of a solid. 

 Glass and ice cannot be made to stick thus together, neither can 

 glass and glass, nor alum and alum, nor nitre and nitre, at com- 

 mon temperatures. I have, moreover, placed pieces of ice together 

 over night, and found them in the morning so rigidly frozen 

 together, that when I sought to separate them, the surface of 

 fracture passed through one of them in preference to taking the 

 surface of regelation. Many sagacious persons have also sug- 

 gested to me that the ice transported to this comitry from Norway 

 and the Wenham Lake may possibly retain a residue of its cold, 

 sufficient to freeze a thin film enclosed between two pieces of the 

 substance. But the facts already adverted to are a sufficient 

 reply to this surmise. The ice experimented on cannot be re- 

 garded as a magazine of cold, because parcels of liquid water exist 

 within it. 



44. Nevertheless, as our present knowledge of the facility with 

 which ice permits heat to pass through it by conduction is, as 

 far as I know, absolutely null, I was glad to avail myself of an 

 opportunity which presented itself of obtaining some approximate 

 notion of this power. I owe this opportunity to the kindness of 



* It is here implied that the contact of the moist surfaces must be so 

 perfect, or, in other words, the liquid film betvveeu them must be so thin, 

 as to enable the molecules to act upon each other across it. The extreme 

 tenuity of the film may be inferred from this. A thick plate of water within 

 the ice would facilitate rather than retard licpiefaction. 



t On this point see the paj)er referred to at the commencement. 



