ANTHRACITE COAL MEASURES. 243 



geologists, as already stated, are contained in for- 

 mations of the period of the graywacke group. 

 They extend, according to Professor Rogers, more 

 than 42,000 feet in depth. It will be recollected 

 that we described three distinct mountain ranges, 

 extending through the Middle and Southern States, 

 as, 1. The Blue Ridge System on the east; 2. The 

 Alleghany on the west ; and between these, 3. The 

 Appalachian, consisting of a wide belt of parallel 

 mountain ridges, with deep intervening valleys. 

 Now it is the rocks of this region that constitute 

 the oldest fossiliferous group of the United States, 

 and that contain the anthracite coal ; and because 

 they are next in the descending order to those con- 

 taining the bituminous coal, they are regarded as 

 equivalent to the class of strata in Europe known 

 as the graywacke group. But whether they are 

 or not is of no great consequence. The anthracite 

 coal-fields embraced in these strata, so far as yet 

 discovered, lie chiefly to the northeast of the Sus- 

 quehanna River. If we trace a parallelogram, one 

 line following the Kittatinny or Blue Mountains 

 from the Water Gap of the river Lehigh to the Sus- 

 quehanna, another from that mountain up that last 

 river to its north branch, and a third along the north 

 branch and its tributary, the Lackawanna, till we 

 reach a point almost due north from the point we 

 started from, we shall then enclose nearly all the 

 genuine anthracite seams hitherto discovered in 

 Pennsylvania. Then, to form a correct idea of the 

 situation of the coal, we have only to imagine that 

 a set of strata, conglomerates, grits, shales, and thick 

 beds of dnlhracite, were deposited on some wide 

 and nearly horizontal plain, and not collected, as ap- 

 pears to have occurred with many coal-fields, into 

 troughs or basins previously formed. Then con- 

 ceive the whole of this level once to have been con- 

 verted into an undulating surface of valley, hill, and 

 mountain, by some general disturbing c«inse. W© 



