FROSTBURG COAL FORMATION. 95 



No. Thickness, Name. 



30. 1.5 Stratified iron ore, sp. gr. 3.255. This closely 

 resembles some of the ores of South Wales, and 

 has calcareous spar irregularly interspersed 

 through the mass. 



Slate clay. 



Coal, 



Stratified iron ore, sp. gr. 3.541. 



Coal. 



Shale, 



Stratified iron ore, sp, gr, 3.473, 



Slate. 



Stratified iron ore, sp. gr. 3.374. 



Shale. 



Iron ore in layers, alternating with slate sp. gr. 

 3.374. 



Shale. 



Iron ore, similar to No. 40, alternating with shale 

 or soft slate, 



43. 4.5 Iron ore, similar to No. 40, alternating with hard 



slate. 



44. 1. Coal. 



45. Indurated ferruginous black slate, thickness un- 



known. 



The last brings us down to the surface of the valley, where 

 the excavations were discontinued, and below this the beds 

 have not been much examined ; it is, however, known that a 

 bed of coal 6 feet in thickness crops out near the Potomac, 

 about 600 feet below the 14 feet bed, and that several small 

 beds occur above and below this 6 feet bed.* 



The coal of all the beds is analogous in some respects to 

 that of Wales, and may be ranked among the dry coals, the 

 volatile matters being 15 to 20 per cent.; the 14 feet bed 

 appears to be free from sulphuret of iron, of which there are 

 some slight traces in the smaller beds. 



The quality of those above the 14 feet bed has not been 



* Since the foregoing was written, I have met with a bed of limestone, slightly 

 ferruginous and about six feet in thickness, situated about twenty feet below No. 

 45. Also one of greater thickness and free from iron, about fifty feet lower than 

 the last. 



