INTRODUCTION b( 



arrangement had been placed almost midway in the Lower Barren 

 measures.* 



In 1870 Professor John S. Newberry divided the Ohio Coal Measures 

 into Lower and Upper, including in the former all beds below the Pitts- 

 burg coal to practically the bottom of the Pottsville. Professor Edward 

 Orton adopted this classification in his elaborate discussion of the Ohio 

 coals, published in 1884. f 



In the same year Stevenson employed the terms Lower and Upper for 

 the Coal Measures of northern West Virginia, drawing the plane of sepa- 

 ration just under the Pittsburg coal bed, but including only rocks above 

 the Pottsville. In 1872 he grouped the deposits into 



Upper Barren group, 

 Upper Coal group, 

 Lower Barren group, 

 Lower Coal group, 



the last two being equivalent to XIII and XIV of W. B. Eogers and the 

 first two equivalent to the higher groups of H. D. Rogers, as published in 

 the final report. J 



Toward the end of 1875, in the first of the Pennsylvania reports, Mr 

 Franklin Piatt divided the Pennsylvania Coal Measures into 



Upper Barren measures ; 



Monongahela, from Washington coal bed to Pittsburg coal bed; 

 Conemaugh, bottom of Pittsburg to bottom of Mahoning sand ; 

 Allegheny, bottom of Mahoning sandstone to top of Pottsville; 



using names originally employed by Professor Rogers, but not in the 

 same sense. § 



In 1876 Stevenson used the same grouping as in 1872, with a slight 

 change in nomenclature, thus: 



f Greene County group. 

 Upper Barren series j Washington County group . 



Upper Productive series. 

 Lower Barren series. 

 Lower Productive series. || 



In the next year, Mr Piatt modified his classification materially, his 

 new grouping being 



* H. D. Rogers : Geology of Pennsylvania, vol. ii, pp. 477, 500, 503. 

 t J. S. Newberry : Rep. Prog. Ohio Survey for 1870, p. 15. 



i J. J. Stevenson : Regents' Report of West Virginia University for 1870, p. 47 ; 

 Trans. Am. Phil. Soc, vol. xv, p. 15 et seq. 



§ F. Piatt : Second Geol. Survey of Pennsylvania, Report H, p. 8. 

 II J. J. Stevenson : Report K, pp. 34 et seq. 



