Refei'ences to North American Localities. 155 



(probably extending into it) here our state geologists ought to 

 search for the true has. 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 th-e 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- 

 erophou, 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 merely learned that it was entitled to 

 particular examination. 



Limit betvjeen 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, &c. which must have been washed in, 

 by waters elevated beyond the limit of any existing cause. Hence 

 it must have been caused by a deluge. 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 of similar materials with 

 that of the great diluvial 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 is a yellowish gray, or grayish ^^ellow 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. 



