No. 50.] 
437 
nued to be an outlet till the level of this sea was reduced below 890 feet 
above the ocean. Now we find the depth of Cayuga lake to be less 
than 400 feet, and that of Seneca lake more than 500 ; both are exca- 
vated in the same rock. 
In tracing these valleys we find them all continuing southward, and 
beginning at the north we find the greater part of them tending towards 
the Susquehannah, which no doubt at a very early period found an out- 
let to the inland sea. The valleys of Cayuga, Seneca, Crooked, Ca- 
nandaigua, Honeoye and Hemlock lakes,all communicate with the Sus- 
quehannah, by the Chemung and Conhocton rivers. 
The most extensive, and well defined valley west of Seneca lake, 
is the Genesee. The term Genesee valley, is usually applied to that 
portion between Rochester and Dansville, this maintaining nearly the 
same elevation ; that followed by the Genesee south of Portage, being 
a distinct valley. The conditions under which this valley has existed, 
will be an explanation for the others, as they have nearly all been 
more or less under the same influences. In whatever manner we choose 
to explain the production of this valley, we must admit that it is a val- 
ley produced by excavation, and that this portion of country was origi- 
nally covered by rocks, which formed continuous strata with those now 
seen on either side. From all facts yet observed, it appears that such 
valleys have been excavated by violent and powerful inundations, which 
have torn up rocky strata, and carried forward the materials to places 
farther south. The course of the advancing or excavating wave in this 
case, was from nearly north to south, passing all that portion in Li- 
vingston county from Rochester to Dansville, when its course is well de- 
fined. Beyond this point it passed southevsterly by way of Arkport, 
Hornellsville, Canisteo, &;c. to the Chemung river, and thence to the 
Susquehannah. This valley could never have formed an outlet for the 
inland sea for any length of time, for its elevation between Dansville 
and Hornellsville, is more than 1,100 feet above the ocean. It is here 
very obvious, that the original valley did not follow the course now 
taken by the Genesee river, for we find that stream descending to the 
level of this valley from Portage, by falls and rapids of more than 500 
feet. 
It would appear that the excavating wave divided near the junction of 
the Caneseraga and Cashaqua creeks ; the larger portion excavating 
the valley to Dansville, Hornellsville, &c. the other by Portage and 
A 
