228 Geological Society. 



The thinning out of the grits and conglomerates of the west causes 

 the beds of anthracite to be brought more nearly together in this 

 district ; and Mr. Lyell says, the decrease in the thickness of the in- 

 tervening strata prepares the observer for the union of several of the 

 seams still farther east, and for the enormous thickness of the anthra- 

 cite at various places near the village of Mauch Chunk, or Bear 

 Mount, particularly at the well-known Lehigh- Summit Mines. At 

 this point a mass of anthracite forty feet thick, deducting three in- 

 tercalated fire-clays and a fine thin vein of impure coal, is quarried 

 in open day, a covering of forty feet of sandstone being entirely re- 

 moved. In the south mine, where there is a sharp anticlinal fold in 

 the coal, the Stigmaria-clay, four feet thick, was well seen, with 

 nearly forty feet of coal above it and four below. In the Great mine 

 Mr. Lyell observed the following section : — 



Top, yellow quartzose grit. 



Coal, two or three inches of the uppermost part of the 

 bed being in the state of dust, as if they had been 

 crushed or rubbed by the yellow quartzose grit 5 feet. 



Blue fire-clay with Stigmarise 15 inches. 



Coal, including two or three seams of an impure slaty 



nature 25 feet. 



Blue fire-clay with Stigmarise 2 feet. 



Coal, with an intervening layer of hard, bituminous slate 8 feet. 



The anthracite, as in other parts of these coal-measures, often 

 exhibits a texture exactly like that of charcoal ; and frequently im- 

 pressions of striated leaves, exactly resembling, as pointed out by 

 Prof. Rogers, those of liliaceous plants, particularly the iris. 



Mr. Lyell, accompanied by Prof. Rogers, afterwards examined the 

 Room Run mines, on the Nesquahoning, where he saw a splendid 

 exhibition of Stigmarise in a bottom clay, one stem, about three 

 inches in diameter, being no less than thirty-five feet in length. In 

 the roof of slaty sandstone were impressions of Pecopteris, Glos- 

 sopteris, and other ferns. 



At Beaver Meadow, or the middle coal-field, a bed of anthracite is 

 overlaid as well as underlaid by Stigmaria blue clay ; the upper fire- 

 clay, however, soon thins out, and is replaced by sandstone. No coal 

 rested upon it, but Mr. Lyell observes that the carpeting of coal 

 may not be always large enough to cover the flooring of fire-clay, or 

 some change of circumstances or denudation may have interfered 

 with the usual mode of deposition. Upon the whole, Mr. Lyell 

 says, the accumulation of mud and Stigmarise was, in Pennsyl- 

 vania as in South Wales, the invariable forerunner of the circum- 

 stances attending the production of the coal-seams. The two ex- 

 treme points at which he observed the Stigmaria- clay, Blossberg and 

 Pottsville, are about 120 miles apart in a straight line, and the ana- 

 logy of all the phsenomena at those places, and still more on both 

 sides of the Atlantic, is, he says, truly astonishing. In conclusion, 

 Mr. Lyell states, that he had just received a letter from Mr. Logan, 

 announcing the existence of the bottom clay, with Stigmarise, in 

 Nova Scotia ; and that Mr. Logan had visited Mauch Chunk. 



