41'i Carboniferous System of the United States. 



XXXVI. — On the Extension of the Carboniferous System of 

 the United States, so as to include all true Coals. 



By R. p. Stevkns. 

 Read December 16, 1861. 



It will be recollected, that the late Prof. Eaton, and other 

 earlj geologists of our country, considered the Onondaga lime- 

 stone, including the Cherty beds, commonly called the pyri- 

 tiferous limestone of Eaton, to be equivalent to the Mountain 

 limestone of the English authorities ; and as there was at that 

 time a very prevalent contagion among American geologists to 

 trace equivalents of American strata with European, all above 

 this horizon of limestone would naturally fall into the carbo- 

 niferous sj'stem. 



As the geological investigations of New York and Pennsyl- 

 vania progressed, it was found that this horizon of rock strata 

 was low down, nearly at the base of the Devonian, and that the 

 whole thickness of the Catskill Mountains (Hamilton, Portage, 

 and Chemung groups), did actually lie between this limestone 

 and the coal of Pennsylvania ; and that this vast thickness of 

 sedimentary rocks was greatly increased, travelling south-west- 

 wards from these mountains, until in south-western Virginia 

 they had attained their maximum development. 



By the united labors of the brothers Rogers, and their very 

 able assistants, certain vast deposits of conglomerates were 

 placed at the base of the Carboniferous, called by them " For- 

 mation No. XII." — or the Coal Conglomerate, in contradistinc- 

 tion from other conglomerates lying both above and below this 

 very certain horizon. 



This stratum was well defined in the anthracite region of the 

 Schuylkill river, the semi-bituminous region of the Broadtop 

 mountains, and Blossburgh ; also in the bituminous coal regions 

 west of the Alleghany mountains. Tliis conglomerate was con- 

 sidered to be equivalent, if not identical, with the Coal Conglo- 

 merate of the English coal measures. 



