94 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



Mr. Andrew Roy, 1 in 1876, reported that the Mahoning Valley coal 

 region lying in the northern part of the Ohio coal field belongs to the 

 "lower coal of the Lewis No. 1 of the Ohio Geological Survey," and 

 has a varying thickness from an inch to 6 or 7 feet. This deposit rests 

 upon the " Waverly" sandstone, which is so folded as to form numer- 

 ous troughs, in which the coal has reached its maximum thickness. The 

 synclinals were probably formed by erosion anterior to the formation 

 of the coal vegetation, and not by the mountain-building forces exhib- 

 ited in the anthracite fields of Pennsylvania. 



In the year 1876 there appeared, as one of the volumes of the Second 

 Geological Survey of Pennsylvania, the " Historical Sketch of Geolog- 

 ical Explorations in Pennsylvania and other States, by J. P. Lesley, 

 the State geologist." 2 This was reprinted without revision in 1878. It 

 contains so much of interest to the readers of this essay that I refer 

 them to it without abstracting its contents. 



Chapter I is entitled " Early Observations of the Geology of Penn- 

 sylvania." 3 Titles of papers and comments on some of them are given 

 dating back to 1780. 



Chapter II is entitled " The Geological Society of Pennsylvania; and 

 what it did to bring about the first geological survey of the State." 4 



Chapter III, " A history of the first geological survey of Pennsyl- 

 vania," 5 an elaborate description of the "Final Report of 1858," occu- 

 pying pages 134 to 197. 



Chapter IV is "A sketch of the history of other State geological 

 surveys in the United States, aud of their relations to that of Pennsyl- 

 vania." 6 The press of other duties prevented the author from complet- 

 ing this chapter; only one State, that of North Carolina, is discussed. 



In these chapters may be seen an account of the development of the 

 knowledge regarding the geology of Pennsylvania up to the close of 

 the first survey and publication of the final report in 1858. The new 

 survey, begun in 1874, in matters of correlation adopted the classifica- 

 tion of the first survey, but modified and amplified its nomenclature. 



With the opening of the Second Geological Survey of Pennsylvania, 

 Mr. Franklin Piatt was engaged as assistant to work up the bituminous 

 coal fields of western Pennsylvania. As a working scheme of classi- 

 fication and nomenclature he modified the scheme of the first survey 

 as published in the final report of 1858 to adapt it to results of the in- 

 vestigations of the year 1874, and published in Report 7 of Progress H 

 the following scheme of Coal Measures and underlying formations : 



1 Roy, Andrew : The Mahoning Valley coal regions. Trans. Amer. Inst. Mining Eng., vol. 4, 1876, pp. 

 188-190. 



2 Geol. Survey of Pennsylvania, Rep. of Progress. Report A: A history of the first Geological 

 Survey of Pennsylvania from 1856 to 1858, by J. P. Lesley ; pp. 226. 1876. 



* Pp. 3-28. 



4 Pp. 29-52. 



6 Pp. 53-197. 



8 Pp. 198-200. 



'Second Geol. Survey of Pennsylvania, 1874. Report of Progress in the Clearfield and Jefferson 

 district of the bituminous coal fields of western Pennsylvania, by Franklin Piatt, Harrisburg, 1875. 



