CAUSE OF GLACIER MOTION. 257 



will then fall short of that which had been expended in 

 melting by an amount which is exactly the equivalent 

 of the work performed. The equation will be thus: — 



Heat expended in melting = Heat evolved in 

 re-freezing + Work performed. 



A portion of the heat expended in melting is thus 

 transformed into work. Now, if the motion of a 

 glacier be mainly due to the expansive force exerted 

 by the melted particles of the ice during their solidifi- 

 cation, then the original source of this motion must be 

 the heat received from the sun. Glacial motion must, 

 therefore, in so far as it is the result of regelation, be 

 transformed heat, or, in other words, molecular motion 

 transformed into glacier motion. 



