walcott.] CORRELATION 393 



Andes. Some were formed at the bottom of the soa by volcanic fires, others have 

 arisen from various causes since the great deep retired. 



During the deluged state of the earth many species of animals were probably de- 

 stroyed. For we continually find the petrified remains of species of animals now 

 totally extinct. 



From the latter observation it is quite evident that at that time he 

 did not consider fossils to be of any value in the correlation of the 

 rocks. In the next edition of the Index ' his theories of the origin and 

 first condition of the surface and position of the rocks are omitted, and 

 a more thorough description is given of the various rock masses, the 

 classification of which was lithologic and based on the views of Dr. 

 ^ Werner. His more extensive work of 1824 2 shows that the correla- 

 tions made between the rocks of the Hudson and those west of the 

 Hudson, along the line of the Erie Canal, were based mainly upon their 

 lithologic characters. For instance, the Calciferous saudrock of the 

 Mohawk Valley, in the vicinity of Little Falls, New York, was traced 

 westward in the vicinity of Utica and eastward down the Mohawk 

 Valley to the vicinity of Schenectady, and then correlated with a Cal- 

 ciferous sandrock on the east side of the Hudson. This correlation 

 was made upon the lithologic character and the stratigraphic succes- 

 sion of the rock masses. Its defective character is shown by the fact 

 that the Calciferous sandrock east of the Hudson is of Lower Cam- 

 brian age and that west of the Hudson is of Silurian (Ordovician) age. 



Classification and correlation on the basis of lithologic character and 

 stratigraphic succession was continued by Prof. Baton iu his work of 

 1828 3 and again in his text-book of 1830. 4 On the map accompany- 

 ing the latter all the quartzose formations are colored yellow, all the 

 calcareous formations blue, the variegated sandstones red, and the sub- 

 ordinate rocks green. By this the primitive limestones of the Adi- 

 rondacks (Algonkian), the Lower Cambrian limestones of Washington 

 County, the CalciferousChazy-Trenton limestones of the central por- 

 tions of the State, and the Lower Devonian limestones of the Upper 

 Helderberg are all placed under one color. 



In 1832 5 he introduced a new heading into his Text Book, as follows: 

 ' " Organized remains as auxiliaries in the determination of rock strata." 

 Under this he says : 



The remains of similar species of animals and plants are found emhraced in similar 

 series of rocks ; and these occurrences are so uniform that rocky and earthy strata 

 may be determined by them. 6 



•An Index to the Geology of the Northern States, 2d ed., 1820, pp. 286. 



2 A geological and agricultural survey of the di»trict adjoining the Erie Canal, 1824, pp. 163. 



3 Geological nomenclature, exhibited in a synopsis of North American rocks and detritus. Am. Jour. 

 Sci., vol. 14, 1828, oppo. p. 144, pp. 145-149, 359-368. 



4 Geological text-book, prepared for popular lectures on North American geology; witb applications 

 to agriculture and the arts. Albany, 1830, pp. 64. 



'Geological text-book for aiding the study of North American Geology; being a systematic ar- 

 rangement of facts, collected by the author and his pupils, under the patronage of the Hon. Stepheu 

 Van Rensselaer. 2d ed. Albany, 1832. 



*0p. cit., p. 25. 



