williamb.] JAMES HALL. 67 



The author in the main agreed with American geologists in the line of 

 division between these two great groups of rocks. He then correlated 

 the system of America with that of Europe, after which he added a tab- 

 ulation of the faunas of both countries, giving references to synonyms, 

 strata, localities, and formation in country. 



In 1848, before the American Association of Geologists and Natur- 

 alists, James Hall presented a paper 1 in which some valuable compari- 

 sons are given of the characters expressed by the rocks as they outcrop 

 in different areas. The Hudson River group was recognized in Ohio, 

 Indiana, Kentucky, and elsewhere in the interior. It becomes more 

 calcareous and is called u Blue limestone n in the more western expos- 

 ures. Hall noticed that it contaius Conchifera in the East with few 

 Brachiopods; that in the West, Brachiopods are conspicuous with Corals 

 and Crinoids, Crustacea, and Trilobites. The Oneida conglomerate, 

 the Medina sandstone, and the Clinton formations of New York were 

 very slightly represented in the Southwest. The Niagara shale and 

 limestone in the East were both fossiliferous ; in their western expos- 

 ures the limestone is reported as thicker and containing abundant 

 Corals, and the calcareous matter is reported as increasing on coming 

 westward. The Onondaga Salt formation thins out on coming west- 

 ward, the Helderberg formations mainly disappear west of New York, 

 except the Upper Limestone, which appears in Ohio, Indiana, and Ken- 

 tucky, but is of lighter color thau its representatives 2 in New York. 

 The Marcellus and the Hamilton formations are reported as sandy iu 

 the East, and the muds diminish and the sands increase in western 

 New York, and in Ohio only the lower, Shale, and this of limited thick- 

 ness appears. The rocks from the Hamilton group upward, and the 

 Old Red sandstone are more sandy in the East, and more argillaceous 

 and thinner westward. The rocks of the Catskill Mountains, called 

 the u Old Red sandstone," also appear in eastern Pennsylvania, but 

 disappear westward, allowing the Coal Measures to rest on the con- 

 glomerate in the East, but in the West, on the Chemung, and still far- 

 ther west on the limestone. 



As a conclusion from these observations the author pointed out that 

 a continent supplying sediments must have existed eastward of the 

 great deposition of sediment along the border, extending from New 

 York through Pennsylvania southward. 



M. Ed. de Verneuil, after a visit to the United States and examina- 

 tion of our formations and their fossils, published in the Bulletin of the 

 Geological Society of France the most valuable paper on correlation 

 which had appeared up to this time. 3 



1 The Geographical Distribution of Fossils in the Ohler Rocks of the United States. 



2 The Corniferous and Onondaga limestone.— H. S. W. 



'Note sur le parall6lisme des roches des depots paleozoiques de l'Aru6riquo septentrionalo aveo 

 ceux de l'Europe, suivie d'un tableau des especes fossiles communes aux deux continents, avec l'indi- 

 cation des Stages ou ellesse rencon trout et termin6 par unoxameu critique de chacune decesespecea. 

 Soc. geol. France, Bull., 2 a ser., vol. 4, 1847, pp. 646-709. 



