102 Mr. Maclure on the Geology of part of N. Amertca. 
. 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 
is continent, such, as the small_number and wild condi- 
uion of the wandering herds found on this part of the conti- 
nent, whencompared 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 flecks of aquatic birds, and 
the very few terrestrial; might be mentioned as some of the 
problems solved by the foregoing supposition. _ ; 
nting 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 thelake, 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, 
ty that the southern sun melted the ice before it got 
so far. : 
