44 IXTRODUCTIOX 



In the annual reports of the Sogers brothers a series of numbers were 

 used to designate their subdivisions of the Paleozoic rocks. The first 

 annual report of Henry D. Eogers, published in 183()/ stated that " the 

 detailed examination of the Appalachian region was begun in the southern 

 part of Bedford County, and prosecuted during the residue of the season 

 in this, and the rest of the counties between the Maryland state line and 

 the Susquehanna Eiver, in one direction ; and in the Cumberland Valley 

 and the ridge of the Alleghany Mountain, in the other." Professor 

 Rogers reported that the rocks of this region instead of being in the 

 Transition class, as generally believed, belonged in the Secondary epoch. 

 He divided the rocks of the Appalachian region into twelve sets of rocks 

 to which he gave Arabic numerals in ascending order, applying 1 to the 

 oldest division, a.nd concluded that " For the classification, the most con- 

 venient and natural arrangement that otters itself, is a subdivision of the 

 entire series into two systems, grouping together the three upper rocks 

 under the name of the Carboniferous- sijftie)i). and the lower nine under 

 that of the Appalachinn system" (Joe. cit. p. 1"^). The rocks considered 

 in this volume as Devonian were described under the numbers 6, 7, 8, and 

 9 ; and in general Xo. 6 included those now called the Helderberg, No. 7 

 the Oriskany, for which Eogers suggested the name " fossiliferons sand- 

 stone," No. 8 the Eomney arid Jennings formations, which he called the 

 "olive state stratum," and No. 9, the Catskill. In Eogers' second 

 annual report, published in 1838, he definitely introduced the name 

 " Fonnation " for each of these divisions, changed from Arabic to Eoman 

 numerals and described thirteen formations. 



This system of classification of the Pennsylvania rocks appears to have 

 been closely followed by William B. Rogers in Virginia and in his report 

 of 1837, published in 1838, he describes the members west of the Blue 

 Ridge. The rocks which are now referred to the Devonian are described 

 under the numbers 6, 7, 8, and 9 and there are frequent references to their 

 exposures to the south of the Potomac River in the northern counties of 

 what is now West Virginia. His report for 1839, published in 1840, cor- 

 rectly referred the arch of Wills Mountain to formation IV and for the 



' Rogers, First Annual Rept. of State Geologist |of Pennsylvania!, 1836, p. 10. 



