DYNAMICAL GEOLOGY. 221 



freezing of water in cracks and other spaces. Scheuchzer is 

 thus the founder of the Theory of Dilatation, afterwards advo- 

 cated by Charpentier and Agassiz. The pastor Altmann in 

 1750, and Gruner in 1760, wrote about glaciers without bring- 

 ing forward anything essentially new. They referred the 

 movement of Alpine glaciers to the sliding of the ice on a 

 sloping base. Neither Scheuchzer nor the two last-named 

 authors had given special attention to the moraines. 



A short paper, published in 1787, by Kuhn in Hopfner's 

 Magazin Jur Helvetiens Naiurkunde, contained not only 

 an excellent description of the Grindelwald glacier and its 

 moraines, but the author also followed the old moraines, and 

 concluded that the glacier had formerly been of far greater 

 extent. De Saussure's famous Book of Travels (1796-1803) 

 contained accurate descriptions of the glaciers in Wallis, the 

 Bernese Oberland, and the Mont Blanc group. The form, 

 arrangement, composition, and movement of the moraines were 

 all carefully handled. Saussure also used the moraines as a 

 means of determining the extent and the advance and retreat 

 of the glaciers, without, however, drawing any general con- 

 clusions. Strange to say, he associated neither the smoothness 

 of the glacier floor nor the " Roches moutonnees " with the 

 movement of ice-masses. 



Saussure had in F. G. Hugi a successor who accomplished 

 much for the knowledge of Alpine glaciers. A fearless moun- 

 taineer, Hugi explored the upper reaches of the glaciers; in 

 1827 he even built a hut on the Finsteraar glacier for his 

 convenience in carrying on researches. He observed many 

 facts about the structure and constitution of the snow, firm, 

 and ice at different heights, about the position of the firm line, 

 about fissures and crevasses which had escaped previous 

 investigators. 



In the year 1821, at the Eighth Annual Congress of the 

 Swiss Society of Scientists, the engineer Venetz read a paper on 

 the variations of temperature in the Swiss Alps, which con- 

 tained wholly new conceptions. This important paper was not 

 published until 1833. Venetz called attention to the fact that 

 there were not only moraines connected with the advances and 

 retreats of the Alpine glaciers, but that in addition to those, 

 morainic walls occurred at a greater distance from the present 

 glaciers, and they gave evidence of glaciation on a scale of 

 enormous magnitude in some former period. In 1829 Venetz 



