Theories of Formation of Coal. 101 



2. Reckoning only the greater divisions, when a difference 

 of mineral character takes place, there are, besides the coal- 

 seams, 340 beds, from a few inches to 190 feet thick, with- 

 out alteration of mineral composition ; involving, in the lat- 

 ter cases, long periods without any change in the nature of 

 the detritus washed into the water where the deposition was 

 going on. 



3. These beds consist of sandstones, arenaceous and argil- 

 liferous slates, and clays, alternating without any apparent 

 order of succession ; sometimes one sometimes another lying 

 upon the coal ; and occasionally, but not frequently, the shale 

 upon the coal is said to be carbonaceous. 



4. Interstratified with these beds are eighty-four seams of 

 coal, from one inch to nine feet thick ; the highest being 

 covered by a series of beds of sandstone, &c. 200 feet thick ; 

 the lowest seam separated from the carboniferous limestone 

 by 1340 feet of similar sandstones and shales, making the 

 coal-hearing strata 5460 feet in thickness. 



5. The seams of coal occur at very unequal distances ; some 

 are separated by a few inches only of shale or sandstone, 

 others by as much as 360 feet. 



6. There are twenty -three seams, occurring in succession, 

 most of which are not distinguished by any term indicating 

 quality ; in two instances, one a three-feet seam, they are said 

 to be bituminous, and several seams are said to be binding, 

 which means the same as caking, a quality which only richly- 

 bituminous coals possess ; the rest are merely called " Coal." 

 These twenty-three seams, with their interstratified sand- 

 stones and shales, occupy 1840 feet. 



7. Then succeed thirteen seams, in a space of 1000 feet 

 and nine of these are described as " not bituminousJ'^ 



8. The thirty- seventh seam, in descending order, is said to 

 be anthracitic, and fourteen seams below it are so designated : 

 then come four seams merely called " Coal," and all very 

 thin. Beneath the lowest of these, and separated by sixty 

 feet of arenaceous shales and sandstones, comes a bed of 

 coal, four feet six inches thick, called Anthracite, with five 

 feet of underclay ; beneath this are seven seams called An- 

 thracite, and three more are intercalated called anthracitic. 



