472 ORIGIN OF THE APPALACHIAN COAL STRATA, 



run, and Brushy ridge, in Virginia. The coal of the Little North 

 mountain, is, however, a true anthracite. All of these coal-fields, 

 and insulated patches of the formation, belong to the most dis- 

 turbed portions of the Appalachian chain, and they are associated 

 with some of the boldest flexures and greatest dislocations of the 

 whole region. The first or southeastern anthracite basin of Penn- 

 sylvania, presents innumerable sharp flexm-es and close plications, 

 with inversion, of the sti*ata. 



Secondly. In the next well-defined range of basins further to- 

 wards the northwest, that namely of the Allegheny mountain, and 

 the general escarpment of which it is a part, the proportion of 

 volatile matter varies usually from sixteen to twenty-two per cent.; 

 but is generally about eighteen or twenty per cent. This belt in- 

 cludes all the coal-fields, situated immediately to the northwest 

 of the Allegheny mountain, in Pennsylvania ; also, the Potomac 

 basin, in nearly the same line, and the coal-fields of the Little 

 Sewell, and the eastern side of the Big Sewell mountain, in Vir- 

 ginia. The position of this belt of the coal-measures is some- 

 what west of the region of steep flexures of the sti'ata, and beyond 

 all the considerable dislocations ; while it embraces a few very 

 extensive, regular, and nearly symmetrical anticlinal axes of the 

 flatter form, distinctive of their intermediate position between the 

 east and west. 



Thirdly. The great Appalachian basin, with its subordinate 

 troughs, forming the wide coal-field watered by the Ohio river 

 and its tributaries, embraces a series of coal-beds, which are all 

 distinguished by a still larger amount of volatile matter. In 

 crossing the breadth of this wide coal-field, we find a very material 

 alteration in the character and composition of the coal. Along 

 its eastern side, or near the last considerable axis of the Appa- 

 lachian chain, the amount of volatile matter is commonly from 

 thirty to thiiiy-five per cent. "Westward of this line, on the Mo- 

 nongahela river, both in Pennsylvania and Virginia, the propor- 

 tion approaches to forty per cent, while still further in the same 

 direction, or near the Ohio river, it ranges from forty to even fifty 

 per cent., according to local circumstances. In this most w^estern 

 or main coal-field, the flexures of the strata are extremely gentle, 



