S53 LECTURES ON GBOLOOT. 



carried down from the high grounds, and deposited over the 

 previous accumulations ; thus producing alternate beds of pebbles, 

 sardstone, shale, and coal, according to their respective densities. 



The enormous size of these plants, as well as the quantity 

 necessary to form so great a thickness of coal, is accounted for by 

 the supposition that the primeval world was more disturbed by 

 volcanic action, and the atmosphere more loaded with carbonic acid 

 and moisture, while the soil was hotter from the proximity of the 

 internal fires than at the present time, even in tropical regions, 

 where alone the congeners of most of the coal plants are now 

 found. 



The inundations alluded to are not uncommon in volcanic 

 countries, produced either by the sudden condensation of the clouds 

 into rain by the electricity evolved during an eruption, or from the 

 melting of the snows crowning the mountain summits, or from 

 river or sea water sucked up and again discharged from the crater. 

 In South America volcanoes exert their ravages less by burning 

 lavas than by torrents of mud and water. In one instance, nearly 

 fifty miles of country were covered with mud containing so much 

 carbonaceous matter that when dry it is used for fuel. A partial 

 mud-flood of this nature would account for the separation of the 

 two upper beds of the ten-yard coal from the rest, by the interpo- 

 sition of a thick bed of shale, at Bloomfield colliery, upon which 

 these two beds recline, cropping out at one extremity, though they 

 join the main coal at the other. The thin laminae, however, which 

 constitute the beds of coal are sufficient to convince us of their 

 gradual deposition in most cases, even if the perfect and uninjured 

 remains of the associated fossil plants did not place it beyond all 

 doubt. It may not be presumptuous to suppose that the pro- 

 digious development of vegetable life that occurred in those early 

 ages of the world, was necessary to free the atmosphere from its 

 superabundance of carbonic acidj and that the consequent accu- 

 mulations of vegetable remains were laid up in the form of coal 

 beds, by a bountiful Providence, for the use of the latest and most 

 noble of the beings destined to inhabit the earth. 



The existence of a stratum of basaltic rock below the coal, many 

 yards in thickness, and identical with the trap of Rowley, and the 

 occurrence of numerous faults, fissures, and basaltic dykes, in the 

 coal strata, are sufficient to prove that subterranean fires were 

 exerting their energies both before and after the formation of the 

 coal. These faults intersect the coal fields in every direction, and 

 many of them are traceable to the Rowley Hills on one side, and 

 to Pouch Hill on the other. Sometimes the strata have merely 

 subsided many yards at the fault, without any separation j but in 

 many cases the faults exist as fissures, filled up with green rock, or 

 basalt and limestone, altered by the eflPects of heat. The Rowley 

 Hills make a breach of very considerable extent into the coal field, 

 being about three miles long, by three-quarters of a mile wide, with 

 an elevation of 900 feet. They are eleven in number, and consist 

 of dark-coloured basalt -, but except at Pearl Hill there is but little 



