1858.] " BEGELATION " EXPLAINED ON M. PERSON'S PRINCIPLES. 231 



This waste has yet to be proved ; but I have little doubt 

 of it ; and it is confirmed by the wasting action of superficial 

 streams on the ice of glaciers, though other circumstances may 

 also contribute to this effect. 



III. The theory explains " regelation." For let a second 

 plane surface of ice A'B' be brought up to nearly physical contact 

 with the first surface AB. There is a double film of " viscid 

 water " isolated between two ice surfaces colder than itself. 

 The former equilibrium is now destroyed. The films AB la and 

 A'B' ~b'af were kept in a liquid or semi-liquid state by the heat 

 communicated to them by the perfect water beyond. That is 

 now removed, and the film in question has ice colder than itself 

 on both sides. Part of the sensible heat it possesses is given to 

 the neighbouring strata which have less heat than itself, and 

 the intercepted film of water in the transition state becomes 

 more or less perfect ice. 



Even if the second surface be not of ice, provided it be a 

 bad conductor, the effect is practically the same. For the film 

 of water is robbed of its heat on one hand by the colder ice, and 

 the other badly-conducting surface cannot afford warmth enough 

 to keep the water liquid. 



This effect is well seen by the instant freezing of a piece 

 of ice to a worsted glove even when on a warm hand. But 

 metals may act so, provided they are prevented from conveying 

 heat by surrounding them with ice. Thus, as has been shewn, 

 metals adhere to melting ice. 



EDINBURGH, 19th April 1858. 



