References to North American Localities. 155 
(probably extending into it) here our state geologists ought to 
search for the true lias. ‘Two miles north of Knox village in Al- 
bany county, is the genuine coral rag, as many foreign geologists 
have decided. This according to Brongniart, is immediately a- 
bove the uppermost of the true Jura limerocks. If our state geol- 
ogists will begin at this rock and descend to Livingston’s Cave, 
making careful comparisons with the organic remains, I think 
. some valuable discoveries may be made. ‘The strata are numer- 
ous and thin. A little below the coral rag is a coarse sandy rock 
which breaks by natural cleavages into most perfect parallelopi- 
peds. It abounds in univalve shells—probably some of the Bel- 
erophon. Livingston’s Cave is in a coarse, harsh, slaty sandrock. 
I have not searched for its organic relics. Being in very ill 
health when I visited it, I ress: learned that it was entitled to 
particular examination. 
Limit between Tertiary and Diluvial deposits (Thalassient and 
Clysmient). 
The most perfect locality for the illustration of this limit, is 
along the Erie Canal from Rome to Pittsford, a distance of 130 
miles. Here we see at short intervals, gorges in the tertiary clay, 
sand or tufa, of greater or less extent and depth. These gorges 
are generally filled or partly filled with diluvial deposits of vegeta- 
ble matter, shells, gravel, é&c. which must have been washed in, 
by waters elevated beyond the limit of any existing cause. Hence 
it must have been caused by adeluge. At low levels, diluvial de- 
posits are- known by their resemblance to those of higher eleva- 
tion. Hence we know, that the city of Troy, N. Y. is chiefly 
built on diluvion ; because it is made up materials with 
that of the great ddgtias trough of Erie canal and of other simi- 
lar deposits; which required a deluge for their construction. We 
have a general diluvial deposit, which I have called a diluvial 
mantle, or ultimate diluvion. This is the last sediment of a gen- 
eral deluge. It isa yellowish gray, or grayish yellow covering 
of all other deposits in all ancient uncultivated forests, _ It is call- 
ed the loam over hard-pan in New Hampshire, Vermont, western 
New York, &c. 
Limit between Diluvial. and Alluvial deposits (Clysmient and 
Alluvient). 
These last deposits (which are all necessarily produced by wa- 
ter of ordinary elevation) are alluvial, unless their analogy of 
character demonstrates them to be diluvial. 
