GEOI.OCiY. 149 



^.scciUiiii vvhelbcr coal may or may not be found by digging, &.c., or 

 whelber, if found, it be of a good quality and will justify the expense 

 and labor bestowed in getting it out for use. 



One of the most interesting circumstances in reference to this min- 

 eral, so valuable, and, in the present state of the arts and manufactures, 

 so essential to man, is its extensive distribution. Jt is found principally 

 between the latitudes of 30° and 60°, in North and South America, in 

 Europe, and in Asia. One of the most extensive coal fields in the world 

 is that of the United States, extending from Eastern Pennsylvania, with 

 some slight interruption in Ohio, to Indiana, and from New York to Ala- 

 bama ; being about eight hundred miles long, and two hundred to four 

 hundred miles wide. In the eastern part of this field, it is of the variety 

 called Anthracite, being hard and burning witliout llame ; in the western 

 part it is soft, bituminous, and burns with a bright flame. This difierence 

 in the character of a mineral, evidently belonging to the same deposit, is 

 ascribed, by some, to the contiguity of igneous rocks, in the East, by 

 which the more volatile parts were driven ollj and by Lyell, to the dif- 

 ference of inclination of the superincumbent rocks, which, being nearly 

 liorizontal west of tlie Allegheny range, would not as easily permit the 

 hydrogen and carburetted hydrogen to escape, as on the East, where the 

 seams and strata are nearly vertical. The decrease of volatile matter in 

 the coal with the increase of the inclination of the strata render.s this 

 opinion highly probable \ alihough it favors the first named opinion no 

 less, for, the disturbance liaving been greatest where there was the great- 

 est action of the subterranean heat, the sublimation of the volatile mat- 

 ter would be most readily effected there. Formerly it was supposed 

 that tlie differences between the several kinds of mineral coal were due 

 to a difference of age, or that they marked diflerent eras in the earth's 

 liistory. But now they are found to be mainly referable to local cause.? ; 

 the great coal fields all over the earth having been formed under sub- 

 stantially the same circumstances, and during the same geological 

 period. 



In confirmation of this opinion it may be remarked, that, not only 

 do thev occupy the same position in the geological series, but, what i.s 

 still more remarkable, they, with slight exceptions, contain the same 

 fossils both animal and vegetable, showing a remarkable nearness to 

 identity of tlie flora and fauna all over the earth at the period of their 

 formation. The reason of the occurrence of the workable coal beds 

 entirely or principally in the present temperate zones is probably to be 

 found in the great and continued heat of the intertropical bell, producing 

 the rapid decomposition of the va&t and luxuriant vegetation, which it 



