THE 



MONTHLY AMERICAN JOURNAL 



OF 



GEOLOGY • 



AND NATURAL SCIENCE. 



Vol. I. Philadelphia, March, 1832. No. 9. 



GEOLOGY, No. 3.— ON THE CONSTITUENT MINERALS, AND THE 

 STRUCTURE OF THE PRIMARY ROCKS. 



Although the exact line which divides the primary rocks 

 from the division called transition, has not yet been universally 

 agreed upon by geologists, yet we conceive this to be in a great 

 measure occasioned by the prevalence of a theoretical opinion, 

 which has drawn their attention too much from characters of a 

 more definite kind, than those depending upon a supposed first 

 appearance of organic remains. If it be true, that there was a 

 moment in the history of our planet, subsequent to the existence 

 of inorganic matter, when organized bodies, vivified by animal 

 and vegetable life, first began to appear, and that the evidence 

 of such appearance is now to be found in the crust of the earth, 

 we conceive, — without denying the reasonableness of this theory 

 — that the substantial proofs of it have not yet been brought 

 forward. It will require a prodigious concurrence of observa- 

 tion, that we cannot reasonably look forward to, in our own 

 time, before a unanimous opinion can be produced, that the 

 lowest bed, in the descending order of the series, has been ascer- 

 tained, which contains organic remains, and that the search 

 need be continued no further. Practical geologists are well 

 aware of the great difficulties attending the establishment of a 

 line, to be considered as the basis of this hypothesis, which has 

 formed so strong a connexion with geology, and which, if it could 

 be demonstrated, would raise it to a very high rank as a science, 

 both for its exactitude, and the dignity it would derive from so 

 remarkal)le an illustration of ant-oeval chronology. 



Vol. I.— 49 385 



