Prof. Johnson's Report on the Bradford Coal Field. 139 



One circumstance worthy of remark in connection with the 

 position of the lower coal bed in the formation, is that in the 

 central portion of the basin, this bed reposes not on a conglom- 

 erate rock nor is it underlaid at all by such material, but rests on 

 a fine grained gritstone five or six feet thick, distinguished from 

 the underlying sand rocks chiefly by its superior compactness and 

 white color. On the borders of the coal basin on the contrary, 

 the underlying rock is a massive conglomerate of coarse pebbles 

 many feet in thickness, capping the otherwise denuded ridges and 

 serving by its great durability to defend the softer rocks below 

 from the action of water and the disintegrating power of growing 

 and decajAJug vegetables. 



The materials collected from the several parts of the Bradford 

 coal field have been submitted to assay by Prof. Johnson, and 

 yielded the following results. 



" Analyses of Coal. — Eight samples of the coal of this region have 

 been examined. 



"No. 1. This specimen is from the fifth ply of coal in the lower bed, 

 opened near the head of Fall creek. Thickness of the ply, 6\ inches. 

 Its specific gravity is 1.5155. 



At a temp, of 300°, it loses of moisture, - 



By distillation at a red heat of water, 



Uncondensable gaseous matter, - - - 



It contains of carbon, . - - - 



And of earthy matter, - - - - 



100.0 



" The ashes are almost perfectly white, and of moderate density. This 

 as well as the two following specimens, is from parts of the bed so near 

 the outcrop as to yield, as in all similar cases, a higher proportion of 

 earthy matter than would be found to exist in the coal when not exposed 

 to any of the decomposing influences of the atmosphere. 



" No. 2. This specimen was from the third ply of coal in the same 

 opening as the preceding. The thickness of this ply is Q\ inches. Its 

 specific gravity is 1.4485. 



At 260° it loses of moisture, - - - 1.9 percent. 



And at a bright red heat it gives of water, - 6.2 " 



of gas, - - 9.3 " 



17.4 



It contains of carbon, - - - - 70.0 



And of earthy matter, - - - - 12.6 



100.0 



