134 Geological Equivalents. 



since.* Here is a case, therefore, where strata may be examined in 

 place throughout a great extent of country ; but intrinsic characters 

 are still required for determining their true position as a general mass, 

 compared with European strata or with those of other districts in 

 America. 



From a consideration of the cases here referred to, intrinsic char- 

 acters, more definite than any left us by Werner, seem to be essen- 

 tial to the progress of the science. The enumeration of mineral con- 

 stituents of rocks, can never be satisfactorily applied. Unorganized 

 matter presents but few characteristics. Naturalists find it a more 

 difficult task to describe, by external characters, about two hundred 

 and seventy species of minerals, than fifty thousand species of plants, 

 and a still larger number of animals. 



It is a subject of high congratulation to students in geology, of our 

 day, that the illustrious Cuvier, aided by the Brongniarts and their 

 coadjutors, have extended the science of organic nature to the science 

 of geology. We are no longer limited to the enumeration of mineral 

 constituents. We find the same organized remains associated with 

 equivalent strata, in every part of the earth ; though they often ex- 

 tend into several adjoining strata, which are probably cotemporaneous, 

 or nearly so. Were every species of organized remains examined, 

 described, and figured ; geologists could correspond as understand- 

 ingly, as botanists can now correspond on the subject of plants. Great 

 progress has been made in the science of animal relics; and the works 

 of Sowerby, Goldfuss, and others, already begin to place students in 

 geology on the real course towards the truth. M. Adolph. Brongniart 

 will soon relieve them from all embarrassment among vegetable fossils. 



As no attempt has hitherto been made for shewing the relation- 

 ship between European and American strata, by a general enumera- 

 tion of the organized remains in American strata, I offer the following 

 imperfect list,f as an attempt towards the establishment of the most 

 important starting points. I confine myself to those strata, which are 

 acknowledged by the geologists of both continents — leaving out all 



* The map referred to was prepared for this Journal, at the expense and direction 

 of Gen. Stephen Van Rensselaer; and will appear in it as soon as I can prepare the 

 necessary explanations. It has been inserted at the end of a small text-book, in a 

 few copies only. 



\ The best specimens found in the shelly variety of carboniferous (metalliferous) 

 lime-rock, and in the second graywacke, (coal grit,) did not arrive in season for this 

 article. Our boxes were detained by a breach in a canal, and other contingencies. 

 1 hope soon to be able to add them, and the specific names of our vegetable fossils, 

 collected chiefly in Pennsylvania. 



