90 CARBON. 



effects of heat besides this debituminisation of the coal ; 

 while the bituminous coal occurs where such disturbances of 

 the rocks have not taken place : and the amount of bitumen 

 increases as we recede from the region of greatest distur- 

 bance. The heat and attendant siliceous solutions have 

 therefore been the means of giving unusual hardness *.o the 

 Rhode Island coal. 



Owing to the various upliftings or foldings of the strata and 

 subsequent denudations, the beds are often exposed to view 

 in. the sides of hills or ridges, and the coal in Pennsylvania is 

 in most cases rather quarried out. than mined. The layers 

 are at times 20 to 35 feet thick, without any slaty seams, and 

 the excavations appear like immense caverns, whose roofs 

 are supported by enormous columns of coal, " into which a 

 coach and six might be driven and turned again with ease." 



Besides the great coal beds of the coal era, as it is signifi- 

 cantly called, there are small beds, sometimes workable, of 

 a more recent date. The bed near Richmond, Va., belongs 

 to a subsequent period ; there are also beds in Yorkshire, 

 and at Brora in Sutherland. Tertiary coal occurs in 

 Provence, and also in Oregon on the Cowlitz. These beds 

 of more recent coals are seldom sufficiently extensive to paj 

 for working, and are often much contaminated by pyrites. 



The amount of anthracite worked in 1820, in Pennsylvania, 

 was only 380 tons ; in 1847, it amounted to more than 

 3,000,000 tons ; and the whole amount of both anthracite 

 and bituminous coal worked in that state, in 1847, was not 

 less than 5,000,000 tons. In Great Britain, the annual 

 amount of coal mined is about 35,000,000 of tons. 



The uses of mineral coal are well known. The Pennsyl- 

 vania anthracite was first introduced into blacksmithing in 

 1768 or 1769, by Judge Obadiah Gore, a blacksmith, who 

 early left Connecticut for Wilkesbarre. It is now employed 

 in smelting iron ores, and for nearly every purpose in the 

 arts for which charcoal was before employed. 



The formation of coke from pit coal, for smelting iron, is 

 done in close furnaces or ovens. After heating up, the coal 

 (about two tons) is thrown in at a circular opening at top, 

 and remains for 48 hours ; the doorway is gradually closed 

 to shut off the air as the combustion increases, and finally 

 the atmosphere is wholly shut off, and in this condition it 



How is coke prepared ? 



