INTRODUCTORY DISCOURSE. 23 



Tolnov, borrowing the ideas of Mitciiill, without acknowledging the 

 obligation, has applied this theory to the United States at large ; and his 

 geological di?ision consists of 



The granite region, 



The region of sand stone, 



The calcarious region, 



The region of sea sand, and 



The region of river alluvions. 



He has in one instance, departed from dr. Mitchill's arrangement by 

 substituting a region of sea sand fora schistic region.* 



These are the principal attempts which have been made to illustrate 

 our geology ; and although entitled to merit they are imperfect ; and, 

 probably, to a considerable extent fanciful. Amid the thirty-eight dif- 

 ferent substances which Mac lure has mentioned as composing the different 

 formations, the others hare designated but five; and although I presume 

 that the denomination given to a particular region is only intended to 

 indicate that the principal rocks or substances are of the kind from which 

 the appellation is derived, yet it must be obvious, that in such an extent 

 of country it is utterly impossible to arrive at such a conclusion without 

 thr most minute and scrutinizing surveys. It is difficult to distinguish 

 and ascertain the different kinds of formations ; it requires considerable 

 practical knowledge to discriminate between matter purely inorganic, 

 and its mixture with organic substances , and as strata of different as 

 well as of cognate species are not only piled upon each other, but are 

 frequently bniied in the bowels of the earth, there is great difficulty in 

 forming just conclusions. This science, and the kindred science of mine- 

 ralogy, have been almost entirely uncultivated with us; and when we 

 consider their immense importance, and the extensive investigation 

 which they open, we must be convinced that we ought to devote more 

 than ordinary attention to their cultivation. 



The aspect or physiognomy of our country is certainly marked by 

 striking and extraordinary characters. The Hudson is the only river in 

 the United States where the tide passes through the alluvial primitive 

 transition, and into the 0aetz formation. In the east we have an ocean of 

 salt water. In the west we have fresh-water seas of immense extent : 

 there is every indication, not only of the recession of lakes, but also of 

 their total exsiccation :(7) hence we have three kinds of alluvial forma- 

 tions : one arising from the retreat of the o^ean. another from the subsi* 

 dence or extinction of lakes : and another from the overflowing, retreat, 

 and change of rivers. Marirfe and vegetable substances are to be found. 



* See the Transactions of the American Philosophical Society, vol. 6. Trans- 

 acnc" jf :'.<.- Society of Arts, held at Albany, vol. 1. j and Volney's View of the 

 Baited States. 



