156 



THE FOKMS OF WATER IN 



392. Many years subsequently, De Charpentier of Bex 

 renewed and developed this theory with such ability 

 and completeness, that it was long known as Charpen- 

 tier's Theory of Dilatation. M. Agassi z for a time 

 espoused this theory, and it was also more or less dis- 

 tinctly held by other writers. The glacier, in fact, was 

 considered to be a magazine of cold, capable of freezing 

 all water percolating through it. The theory was 

 abandoned when this notion of glacier cold was proved 

 by M. Agassiz to be untenable. 



393. In 1760, Altmann and Griiner propounded the 

 view that glaciers moved by sliding over their beds. 

 Nearly forty years subsequently, this notion was revived 

 by De Saussure, and it has therefore been called ' De 

 Saussure's Theory/ or the ' Sliding Theory 5 of glacier 

 motion. 



394. There was, however, but little reason to connect 

 the name of De Saussure with this or any other theory 

 of glaciers. Incessantly occupied in observations of 

 another kind, this celebrated man devoted very little 

 time or thought to the question of glacier motion. 

 What he has written upon the subject reads less like 

 the elaboration of a theory than the expression of an 

 opinion. 



§ 59. Plastic Theory. 



395. By none of these writers is the property of vis- 

 cosity or plasticity ascribed to glacier ice ; the appear- 

 ances of many glaciers are, however, so suggestive of 



