112 Tlie Position of the Cincinnati Gi^oup. 



In Pennsylvania this group is divided into : 1st, The Ponent red 

 sandstone, which is 5,000 feet thick in its southeastern outcrops ; 2d, 

 Vespertine conglomerate and sandstone, which is 2,660 feet in thick- 

 ness, near the Susquehanna. Making the total thickness of 7,660 feet. 

 (Geo. of Penn., vol. i., p. 108.) 



The rocks of Devonian age are therefore 15,235 feet, or nearly three 

 miles in thickness, and are connected together by their interlocking 

 fossil contents, and united with those of Silurian age, precisely as the 

 Lower Silurian Groups are related to each other. 



The Devonian rocks are followed by the Carboniferous, which are 

 divided into : 1st, Lower Carboniferous ; 2d, Carboniferous conglomer- 

 ate ; 3d, Coal measures ; and 4th, Permian. 



The Lower Carboniferous Grouj), in Nova Scotia, consists of reddish 

 and gray sandstones and shales, conglomerates and thick beds of lime- 

 stone, with marine shells and gypsum, having a thickness of 7,636 feet. 

 (Acadian Geo., pp. 118, 127, 178.) Li Pennsylvania it is 3,000 feet ; 

 in Ohio, 640 feet ; in Illinois, 1,500 feet; in Missouri, 1,145 feet, and 

 in Tennessee, 1,250 feet in thickness. On the Island of Bonaventure, 

 it is about 2,000 feet in thickness, or with the Carboniferous conglom- 

 erate, 2,766 feet, and contains the EatoniajJecidiaris, which is found in 

 the Devonian rocks of New York. 



The Carboniferous conglomerate is 1,400 feet in thickness in Penn- 

 sylvania (Pal. of N. Y., vol. iii., p. 59), and entirely thins out before 

 reaching the Mississippi river. It is only from 100 to 200 feet thick 

 in Ohio. 



Prof. Hall says : "it was evidently formed from the fragments of 

 older formations, drifted, water-worn, rounded and deposited with the 

 larger pieces at the base, and the whole cemented together with smaller 

 pebbles and sand. The depth of the formation in Pennsylvania and 

 its thinning out to the north and west shows the current to have been 

 from southeast to northwest, and probably indicates the close proxim- 

 ity of the source in a southeasterly direction. In Michigan the thinning 

 out is toward the south, or in a contrary direction. In Illinois the 

 formation thins out from the west toward the east. The character 

 of this formation, its manner of deposition, the currents which must 

 have existed to distribute it, all indicate that this continent was an 

 archipelago at the era of the Carboniferous conglomerate." 



There is a thickness of 10,000 feet from the summit of the Hamil- 

 ton Group to the base of the coal measures in Eastern Pennsylvania, 

 and 12,000 feet in the Anthracite region, while in the northwestern 

 part of that State, it attains a thickness of only 2,000 feet. (Geo. of 

 Can., 1866, p. 239.) 



