228 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



south base of the Alps were being examined by A. Guyot. 

 Agassiz had asked him to study the former extent of the 

 glaciers and the erratic blocks. The original intention was to 

 publish a work in common which should comprise the results 

 of all the participants in the glacier researches ; Agassiz was to 

 write the first volume on the glacier phenomena proper, Guyot 

 was to write the second volume on the erratic blocks in the 

 Alps, and Desor was to contribute a third volume on extra- 

 Alpine material. Only the first volume was ever published, 

 Agassiz' Systhne Glaciaire, 1847, vv ^ tn three maps and nine 

 folio plates. Guyot went to Princeton, in North America, and 

 placed his 5000 samples of erratic blocks in the Museum 

 there. The most important results of his researches were 

 published, 1843-47, in the Bulletin de la Societe des Sc. naf. de 

 NeuchateL 



When Agassiz had, in 1840, made known his Ice Age 

 theory, he knew the Northern Diluvium only from the litera- 

 ture. A visit to the Glasgow Meeting of the British Associa- 

 tion in 1840 afforded him the opportunity of studying the 

 erratics in the Scottish Highlands. Together with his former 

 opponent, Buckland, whom he completely converted to his 

 views, Agassiz found signs of glacier action widely distributed, 

 old moraines, glacier scratches, roches moutonnees, and he 

 identified in the Scottish " Till " (boulder-clay, ground- 

 moraine) scratched pebbles and the fine clay and sand 

 material which glaciers push forward on the ground as they 

 move. The importance of the scratched pebbles as indications 

 of glacial formations was thus recognised for the first time. 



In his Glacial System^ Agassiz moderated his views on a 

 connected polar ice-mantle over the greater part of Europe; he 

 allowed that the glaciation of the Alps had been distinct from 

 that of the northern lands, and that it had taken place after, 

 and not before the upheaval of the mountain-system. He 

 also accepted the testimony of Rendu and Forbes on the 

 plasticity of glacier-ice, and referred the movement of glaciers 

 to a combination of physical causes of which dilatation was only 

 one. 



The enthusiasm of the Neuchatel glacialists was infective, 

 and for some years glacial studies were highly popular. The 

 physicist, James Forbes, from Edinburgh, went for three 

 summers in succession, 1842-44, to Switzerland to study the 

 movement of glaciers. His results appeared from time to 



