williams.] EATON, CLAPP. 47 



niferous limerock" as the uppermost Transition rock. This he identi- 

 fied further as equivalent to "some part or most of the Grauwaeke 

 group of De la Heche, the Grauwaeke limestones of some English 

 writers, the Grauwaeke slate of Bakewell, and perhaps the Carbonifer- 

 ous rock of Conybeare, and, surely, the Upper Transition (one of the 

 Psammite) rocks of Brongniart." 1 



The limit between the Secondary aud Tertiary, Eaton recognized along 

 the south shore of Raritan Bay, in New Jersey. He says . u Upper- 

 most of the Secondary deposits is the Cretaceous formation most per- 

 fectly characterized, but it contains no white chalk ; the last of the 

 Tertiary is the plastic clay. 2 



There is nothing particular valuable in this article, or new, even at 

 that time, but the particular importance of quoting it is to show how 

 the Werueriaus were beginning to recognize the absolute importance 

 of fossils in determining the relations of deposits. 



In 1841 A. Olapp 3 correlated the "limestone of the Falls of the 

 Ohio" with the Wenlock ofMurchison; it is the " Cliff limestone " of 

 Locke. The " limestone and marls of Madison and Hanover, Indiana" 

 are correlated with the Wenlock; the "Middle and Lower Blue lime- 

 stone and marls" of Cincinnati are correlated with theCaradoc; the 

 "black bituminous shale" at the foot of the Falls is considered as 

 equivalent to the Marcellus shale of New York ; the "Oolitic" and the 

 "Pentreinite limestone" of Troost and Owen, of Kentucky, Indiana, 

 and Illinois are identified as Carboniferous limestone. The author con- 

 sidered the "limestone of the Falls of the Ohio" in its upper portion 

 to be identical with the Ludlow and Wen lock, the lower and middle 

 portion as equivalent to the Niagara limestone and Gypseous shales of 

 New York, and he further correlated the "Cliff limestone" of Locke 

 with the whole of the rocks represented in New York by Niagara lime- 

 stone, Gypseous shale, Water-lime, and Onondaga limestones. This 

 constitutes the total rock deposit between the " Blue limestone and 

 marls of Cincinnati" and the "Black shale" (Marcellus), and is the 

 western continuation, as he says, of the Middle Silurian of Conrad. 

 The 8 feet of fetid subcrystalline limestone immediately underlying the 

 Black shale the author identified with the New York Water lime, and the 

 "Black shale" above it he regards as not equivalent to the Ludlowvillo 

 shale, as was asserted by Prof. Hall, but as lower and the true equiva- 

 lent of the Marcellus shale. 



In 1841 (which was the second year of the association), Edward Hitch- 

 cock delivered the " First anniversary address before the Association 

 of American Geologists in Philadelphia." 4 A few points are interest- 

 ing in this historical sketch, as signifying the progress which geology 

 had made in America up to this time. 



1 Am. Jour. Sci., vol. 39, p. 153. It is now (1890) called the Corniferous limestone. 



2 This limit is apparently the line between the Green sand and the Raritan clays. 



'Geological Equivalents of the vicinity of New Albany, Indiana, as compared with those described 

 Jn the Silurian system of Murchison ; Proc. Phil. Acad, of Sci., vol. 1 1841, pp. 18, 19, 177, 178. 

 *Soo Am. Jour. Sci., vol. 41, pp. 237-275. 



