1 54 Classes of Rocks. 



19. Third Graywacke. 



I propose placing all this vast formation under one gene- 

 ral name for the present, on account of the difficulties and 

 perplexities which would result from any other method. It 

 embraces what have been described by eminent geologists 

 under graywacke, old red sandstone, breccia, pyritous shale, 

 and pyritous grit. A writer in the American Journal of Sci- 

 ence, vol. 4, p. 249, calls most of it sandstone. By referring 

 it to the Erie canal line, where nature seems to have pre- 

 sented her works in the most uniform and simple dress, we 

 find that all those variable layers are above the cornitiferous 

 limerock. This rock may be traced from lake Erie, in fair 

 view, until it bassetts from under the Helderberg and Cats- 

 kill Mountains : Therefore the pyritiferous rock (pyritous 

 shale and grit of England) which bounds the south shore of 

 lake Erie, is the same in the order of superposition, as the 

 vast pile constituting the Catskill and Allegany Mountains. 

 Professor Henry and H. H. Eaton have traced the lake Erie 

 rocks to the Catskill Mountains ; and Mr. N. Goodsell has 

 traced them to the Olean coal mines in Pennsylvania, under 

 the direction of the Rochester canal company. . 



Subdivisions. Pyritiferous slate. On the shores of lake 

 Erie this is the perfect pyritous shale of Whitby in Eng- 

 land. A pupil of mine, Dr. Witherell, has collected and 

 sent to this school every variety of the Whitby rock, with 

 specimens of the bituminous shale, coal, and most of the 

 petrifactions contained in it. They agree in character, per- 

 fectly with this rock. The same bituminous shale, the same 

 pyritous petrifactions, and the same kind of coal, are found 

 here. The coal is in small quantities until we pass the 

 Pennsylvania line ; but it appears in thin layers for many 

 miles along the east shore of Cayuga Lake. This variety 

 retains its characters very perfectly in some parts of the 

 Catskill Mountains near its base. In the Helderberg, six- 

 teen miles S. W. from Albany, the pyrites is quite as abun- 

 dant as at lake Erie. Pyritiferous grit. Under this subdi- 

 vision I include for the present, all the siliceous rocks of this 

 general stratum ; such as the old red sandstone, gray sand- 

 stone, Rubblestone, conglomerate or breccia, red wacke, 

 argillaceous wacke, and the proper compact graywacke. It 

 may be asked, why not consider each of these as a general 

 stratum ? Every geologist, who will visit Catskill Mountain, 



