XXV 



elaborate account of those discovered in the Old Eed Sandstone of the 

 Devonian system. 



In the midst of all this heavy work he entered on other investigations. 

 He had already turned his attention to the vast ice-masses which furrow 

 the sides of the Swiss mountains, and in 1834 made a report on the ob- 

 servations of Hugi concerning the structure of glaciers. In 1837 he had 

 as President to give the opening discourse to the members of the Helvetic 

 Society of Natural History assembled at Neufchatel. It was the cele- 

 brated "Discours surl'ancienne Extension des Grlaciers." In this discourse 

 he carried to their logical conclusion the facts already observed by Yenetz 

 and Charpentier, that boulders are transported and rocks scratched and 

 polished by glacial action ; and inasmuch as Switzerland is strewn with 

 these boulders, and exhibits in many places the scratchings and 

 polishing of rock surfaces, he boldly asserted that the whole of 

 Switzerland and also the northern parts of Europe had been covered 

 in former ages by a sheet of ice of vast thickness. This heresy felL 

 like a thunderbolt on the Assembly. Leopold von Buch, the greatest 

 geologist of that time, lost all control over himself, and severely de- 

 nounced the new theory. When shown the scratched surfaces near 

 Neufchatel, he replied that the slides of the schoolboys had made them ; 

 and he retired at last exclaiming, " O Sancte de Saussure, ora pro nobis." 

 This violent opposition only spurred Agassiz to fresh exertions ; and for 

 eight successive seasons he made a series of explorations in the neighbour- 

 hood of Mont Blanc and in the Bernese Oberland. "With the determina- 

 tion of ascertaining the intimate structure and the movements of ice 

 formations, he established himself in the summer of 1840 on the Median 

 Moraine of the Aar Grlacier, and lodged his party, consisting of Desor, 

 Yogt, Burkhardt, and Celestin Kicolet, under a large block of gneiss. 

 This comfortless abode, which was invaded by frost at night and by 

 trickling water in the daytime, was facetiously called " L'hotel des IS'euf- 

 chatelais." In 1842 a hut was built on the bank which overhangs the left 

 side of the glacier, and this served as a shelter during the remainder of 

 their visits. 



In 1840 and 1841 Agassiz published in Erench and German his 'Etudes 

 sur les Glaciers,' accompanied by fine plates. His 'Systeme Glaciaire,' 

 with its maps and illustrations, did not appear until 1847. 



In the midst of these geological and palaBontological studies Agassiz 

 found time for a series of careful experiments in moulding. In 1839 his 

 paper appeared, " Sur les Monies de Mollusques vivans et fossiles." In 

 this paper he showed that the soft parts of Mollusca impress their form 

 on the interior of the shell, which form can be reproduced by a cast whose 

 inequalities will represent those of the original animal ; so that the casts 

 of mollusks found in great numbers in certain formations could no longer 

 be considered worthless. He first made interior casts of living shells, 

 studied them side by side with the animals, and applied the knowledge of 



