JEAN LOUIS RODOLPHE AGASSIZ. 481 



sition, and it became necessary for Agassiz, if he would prove 

 the correctness of his views, to make the most careful and 

 thorough investigations on living glaciers. For this purpose 

 Agassiz, in company with Desor and several others, made visits 

 in 1838 and 1839 to the glaciers of Mont Blanc and the Bernese 

 Oberland, and in 1840 established himself for the summer on 

 the glacier of the Aar. That year he published his Etudes sur 

 les Glaciers, giving the results of his investigations up to that 

 time. He also visited England, Scotland, and Ireland, and 

 studied the evidences of ice action in those countries. He per- 

 suaded Arnold Guyot, who had been his friend from boyhood, 

 to join him in this work, and after their first season, 1838, divided 

 the work with him and Desor. 



But his labours were not finished. Doubting the sufficiency 

 of the theory of De Saussure that the cause of the motion of 

 the glacier depends upon gravity and inclined to accept the 

 dilatation theory of Scheuchzer, it became necessary for him to 

 examine with care the structure, form, distribution, and rate of 

 motion of the glacier. Thus it was that, in 1841, he began a 

 second series of observations for the purpose of determining 

 these points. He chose, for the theatre of his investigations, 

 the glacier of the Aar, which, by its extent and accessibility, 

 promised the most favourable results. In 1845 he had com- 

 pleted his work, and in 1847 appeared his Systeme Gladaire, 

 which embodied the final results of his researches upon the 

 structure of glaciers, and their effects upon the soil. The re- 

 sults at which he arrived constitute the chief part of the theory 

 of glaciers as accepted to-day, accounting for their formation, 

 their stratification, their blue bands, their movement, their 

 moraines, the grooved or polished surfaces of the rocks over 

 which they pass, and the erratic blocks left where old glaciers 

 have been. Some important additions have been made by 

 Tyndall, and there are a few points on which these two investi- 

 gators disagreed. 



Charles Bonaparte, Prince of Canino, had for several years 

 been planning a scientific journey in the United States, and 

 had invited Agassiz to accompany him. The latter had agreed 

 to the proposal, and, in order to prolong his stay, obtained, 

 through the influence of Humboldt, a grant of 15,000 francs 

 from the King of Prussia. The Prince' was obliged to give up 

 the journey and Agassiz went without him. For the last few 



