CLOUDS AND RIVERS, ICE AND GLACIERS. 1G7 



424. The gist of the Begelation Theory is that the ice 

 of glaciers changes its form and preserves its continuity 

 under pressure which keeps its particles together. But 

 when subjected to tension, sooner than stretch it breaks, 

 and behaves no longer as a viscous body. 



§ 62. Cause of Reg elation. 



425. Here the fact of regelation is applied to explain 

 the plasticity of glacier ice, no attempt being made to 

 assign the cause of regelation itself. They are two en- 

 tirely distinct questions. But a little time will be well 

 spent in looking more closely into the cause of regelation. 

 You may feel some surprise that eminent men should de- 

 vote their attention to so small a point, but we must not 

 forget that in nature nothing is small. Laws and prin- 

 ciples interest the scientific student most, and these may 

 be as well illustrated by small things as by large ones. 



426. The question of regelation immediately connects 

 itself with that of ' latent heat/ already referred to, (383) 

 but which we must now subject to further examination. 

 To melt ice, as already stated, a large amount of heat 

 is necessary, and in the case of the glaciers this heat is 

 furnished by the sun. Neither the ice so melted nor 

 the water which results from its liquefaction can fall 

 below 32° Fahrenheit. The freezing point of water and 

 the melting point of ice touch each other, as it were, 

 at this temperature. A hair's-breadth lower water 

 freezes ; a hair's-breadth higher ice melts. 



