Ch. XXV.] 



APPALACHIAN" COAL STEATA. 



393 



to e, section, fig. 505, p. 390), is remarkable for its vast area ; for, ac- 

 cording to Professor H. D. Rogers, it stretches continuously from N. E. 

 to S. "VV., for a distance of 720 miles, its greatest width being about 180 

 miles. On a moderate estimate, its superficial area amounts to 63,000 

 Bquare miles. 



This coal formation, before its original limits were reduced by denu- 



