448 LOUIS AGASSIZ. 



soon becomes convinced that the ocean has 

 partially covered and more or less remodeled 

 them. In certain places there are patches of 

 stratified sand interposed between masses of 

 glacial drift-deposit ; elsewhere, banks of sand 

 and pebbles crown the irregularities of the 

 glacial deposit, or fill in its depressions ; in 

 other localities the glacial pebbles may be 

 washed and completely cleared of mud, re- 

 taining, however, their markings; or again, 

 these markings may have disappeared, and 

 the material is arranged in lines or ramparts, 

 as it were, of diverse conformation, in which 

 Mr. Desor recognized all the modifications of 

 the " oesars " of Scandinavia. The disposi- 

 tion of the oesars, as seen here, is evidently 

 due entirely to the action of the waves, and 

 their frequency along the coast is a proof of 

 this. In a late excursion with Captain Davis 

 on board a government vessel I learned to 

 understand the mode of formation of the sub- 

 marine dikes bordering the coast at various 

 distances, which would be cesars were they 

 elevated ; with the aid of the dredge I sat- 

 isfied myself of their identity. With these 

 facts before me I cannot doubt that the oesars 

 of the United States consist essentially of 

 glacial material remodeled by the sea ; while 



