142 Prof. Johnson's Report on the Bradford Coal Field. 



" Thus it appears that the quantity of volatile matter in this coal, is 

 sraall compared with that of most other bituminous coals of our country. 

 Being situated on the eastern extremity of the first principal range of bi- 

 tuminous coal formations west of the Susquehanna river, it adds another 

 to the many evidences which have been derived from my own experiments 

 in proof of the proposition long since advanced, that the quantity of vol- 

 atile matter in the coals of Pennsylvania, and other states, gradually in- 

 creases as we advance from the Atlantic region across and beyondthe Al- 

 leghany mountain, over the great coal fields of 4he western and north- 

 western states. 



" This law becomes the more striking when the anthracite fields are 

 embraced with the bituminous, for there we have a series commencing al- 

 most at zero, and proceeding upwards in the scale of volatility, till, in 

 some of the coals of Kentucky, Illinois, &c., it attains a maximum of 48 

 or 50 per cent. The circumstance of possessing but a moderate share of 

 bituminousness, is favorable to the application of the coals of this region, 

 to the purposes of iron manufacture, and though the per centage of earthy 

 matter is higher than that of some other coats, yet it will be recollected 

 that nearly all the samples are taken from points near the outcrop of the 

 respective beds, and that consequently the relative proportion of earthy 

 matter is likely to be higher than would result from the coals taken a few 

 hundred feet from the edge of the same beds. 



" Iron Ores. — The argillaceous carbonate of iron is the principal vari- 

 ety to be expected in all coal districts. The Carbon creek formation is 

 found in this respect to sustain the general character of all our Pennsylva- 

 nia coal fields, yielding ores in considerable variety, and of different de- 

 grees of richness, capable of producing from six or eight, to forty or fifty 

 per cent, of metallic iron. These ores have been found either in place in 

 the solid strata, or scattered in rolled pebbly masses, over so great an ex- 

 tent as to leave no doubt of their constituting, originally, regular portions 

 of the formation. Thus I have collected samples from the heads of Fall 

 creek, and from those of Long valley, as well as along the channel of the 

 latter tributary; they are also met with in Wagner's Lick creek, and es- 

 pecially on the heads of the latter stream, where the ore has been fully 

 exposed a few hundred yards from Mason's coal mines. Kidney ore is 

 found in several places directly overlying the upper bed of coal. 



*' The lowest stratum of ore which I have been enabled to examine, is 

 situated 1016 feet above the level of the Susquehanna. It constitutes a 

 bed S7^ inches thick, reposing on a bed of fire-clay, 16 inches thick, and 

 covered with a ferruginous shale, 6 inches thick. From this statement, 

 it will appear that the mining of this ore will be effected without any unu- 

 sual difficulty. 



" In the solid part of the stratum, where the influences of the weather 

 have not interfered with its natural state, it is of a light blue color, of ir- 



