308 LOUIS AGASSIZ. 



and grooves ; the polished surfaces, the roches 

 moutonnees ; the rocks, whether hard or soft, 

 cut to one level, as by a rigid instrument ; the 

 unstratified drift and the distribution of loose 

 material in relation to the ancient glacier- 

 beds, — all agreed with what he already knew 

 of glacial action. He visited the famous 

 " roads of Glen Roy " in the Grampian Hills, 

 where so many geologists had broken a lance 

 in defense of their theories of subsidence and 

 upheaval, of ancient ocean -levels and sea- 

 beaches, formed at a time when they believed 

 Glen Roy and the adjoining valleys to have 

 been so many fiords and estuaries. To Agas- 

 siz, these parallel terraces explained them- 

 selves as the shores of a glacial lake, held 

 back in its bed for a time by neighboring gla- 

 ciers descending from more sheltered valleys. 

 The terraces marked the successively lower 

 levels at which the water stood, as these bar- 

 riers yielded, and allowed its gradual escape.^ 

 The glacial action in the whole neighborhood 

 was such as to leave no doubt in the mind of 



^ For details, see a paper by Agassiz on " The Glacial The- 

 ory and its Recent Progress " in the Edinburgh New Philo- 

 sophical Journal, October, 1842, accompanied by a map of 

 the Glen Roy region, and also an article entitled " Parallel 

 Roads of Glen Roy, in Scotland," in the second volume of 

 Agassiz's Geological Sketches. 



