636 PHYSICAL PROPERTIES OF ICE. 



melted below 32° F. ; so that if pieces of ice rather below 32° F. be 

 placed in a mould and pressed, tlie portions of the ice which press 

 against one another will melt, and so the pressure will be relieved. 

 In consequence of the removal of the pressure, the water will freeze 

 again, since its temperature is below 32° F., and the pieces will be 

 frozen together and take up a new form ; this may be again 

 moulded in the same way into new forms in consequence of the 

 alternate melting of the ice by pressure, and its regelation when 

 the pressure is removed.] 



(Reference should be made to Tyndall's " Glaciers of the Alps " 

 on this and on other questions connected with glacier-ice.) 



In his narrative of the voyage, Dr. Kane says : — 



"In Wellington Channel our ice had not acquired its full 

 firmness and tenacity ; its structure was granular and almost 

 spongy, its mass infiltrated with salt water, and its plasticity such 

 that it crumbled and moulded itself to our form under pressures 

 which would otherwise have destroj^ed us. 



" By the time we had reached the middle of Barrow's Strait* 

 and the winter's midnight of December had darkened around us> 

 our thermometers indicating a mean of 15° and 20° below zero, the 

 ice attained a thickness of three feet, with an almost Jiinty hard" 

 7iess, and a splintery fracture at right angles to its horizontal 

 plane. Such ice was at its surface completely fresh, and, when 

 tested with nitrate of silver, gave not the slightest discolouration."] 



(Chapters XLII. and XLIII. contain an account of remarkable 

 changes in the floe-ice in Baffin's Bay). 



Dr. Kane discovered that the floes "which had formed in 

 " mid-winter at temperatures below — 30 were still fresh and pure, 

 " while the floes of slower growth, or of the early and late portions 

 " of the season, were distinctly saline. Indeed, ice which only 

 *' two months before I had eaten with pleasure was now so salt 

 " that the very snow which covered it was no longer drinkable." 



" Another element in the disintegration of the floes, of which 

 this was but a preliminary process, struck me forcibly a little 

 later in the season. The invasion of the capillary structure of the 

 ice by salt water from below would act both chemically and 

 mechanically in destroying its structure ; but I am led to believe 

 that, in addition to the actions of simple infiltration, forces allied 

 to endosmosis are called into play." 



" The infiltration of saline water through the ice assists the 

 process of disintegration. The water formed by surface or sun 

 thaw is, by the peculiar endosmitic action which I believe I have 

 mentioned elsewhere, at once rendered salt, as was evident from 

 Baume's hydrometers and the test of the nitrate of silver. The 

 surface crust bore me readily this evening at a temperature of 21° 

 a;id 19°, giving no evidences of thaw. Beneath, for two inches 

 it was crisp and fresh. As I tried it lower, cutting carefully with 

 my bear-knife, it became spongy and brackish ; at eight inches 

 markedly so ; and at and below twelve, salt-water paste. On the 

 other hand, all my observations, and I have made a great many, 

 prove to me that cold, if intense enough, will, by its unaided 



