GEOLOGICAL SOCIETY OP LONDON. 
171 
tremely modern^ considered geologically_, it is impossible to say 
how many tbonsand years may not have elapsed since the Mas- 
todon and other lost species became extinct. They have been 
found at the d^pth of several feet from the surface, but we have 
no data for estimating the rate at which the boggy ground has 
increased in height, nor do we know how often during floods its 
upper portion has been swept away. 
Ohio. — The Ohio river immediately above and below Cin- 
cinnati is bounded on its right bank by two terraces consisting 
of sand, gravel and loam, the lower terrace consisting of beds 
supposed to be much newer than those of the upper. In the 
gravelly beds of the higher terrace teeth, both of the Mastodon 
and Elephant, have been met with. Mr. Lyell was assured that 
a boulder of gneiss, 12 feet in diameter, was resting on the up- 
per terrace, about 4 miles north of Cincinnati, and that some 
fragments of granite had been found in a similar situation at 
Cincinnati itself. These facts show that some large erratics 
have taken up their present position since the older alluvium of 
the Ohio valley was deposited. In travelling northwards from 
Cincinnati towards Cleveland, Mr. Lyell found the northern 
drift commence in partial patches 25 miles from the former city 
and about 5 miles N. E. of Lebannon, after which it continually 
increased in thickness as he proceeded towards Lake Erie. 
New York — Niagara Falls. — In a former paper Mr. Lyell 
alluded to the position of the remains of Mastodon 12 feet deep, 
in a fresh water formation on the right bank of the river Nia- 
gara, at the Ealls. He remarks that if we had not been able to 
prove that the cataract had receded nearly four miles since the 
origin of the fluviatile strata in question, we should have been 
unable to assign any considerable duration of time as having in- 
tervened between the inhumation of the Mastodon, in marl full 
of existing shells and the present period. The general covering 
of drift between Lakes Erie and Ontario is considered to be of 
