102 Mr. Maclure on the Geology of part of M America, 



That the branches or sources of these rivers should have 

 run longer in the mountains than they have in the great ba- 

 sin or lower country, can be satisfactorily accounted for, on- 

 ly by supposing that they had long been wearing down these 

 beds in the high lands before the great basin or lower coun- 

 try emerged from the waters, and that it has been only since 

 the draining of those waters that their accumulated junction 

 in the bed of the great basin under the level country began 

 the formation of the channels they now occupy. 



This conjecture may likewise account for some of the 

 particularities in the state of the animals, originally found on 

 this continent, such as the small number and wild condi- 

 tion of the wandering herds found on this part of the conti- 

 nent, when compared with their neighbours inhabiting the el- 

 evated plains of Mexico ; the great deficiency in Terrestial 

 Quadrupeds, compared with the vast abundance of Beavers, 

 Otters, Muskrats, and other amphibious or aquatic animals ; 

 the great proportion of Gramnivorous and the small number 

 of Carnivorous; the immense flocks of aquatic birds, and 

 the very few terrestrial; might be mentioned as some of the 

 problems solved by the foregoing supposition. 



The accounting for the existence and extinction of the 

 mammoth would not be difficult, by supposing with Mr. Peal 

 that it was not amphibious, and though originally inhabit- 

 ing the southern parts of the great lake, might in summer 

 occasionally emigrate to the north, and leave their bones 

 on the borders; being deprived of its element by the evac- 

 uation of the great lake, might perhaps be considered as 

 sufficient good reason for their extinction. 



The large masses of granite, some of them weighing 

 tons, scattered over the secondary between Lake Erie and 

 the Ohio, while there is not an atom of granite in place near- 

 er than the north side of the lake, would seem to point at the 

 only mode by which they could probably be transported ; by 

 supposing the lake extended thus far, and that the large 

 pieces of floating ice from the north side might carry those 

 blocks attached to them, and drop them as the ice melted 

 in going south ; few or none being found south of the Ohio, 

 shows that the southern sun melted the ice before it got 

 so far. 



