170 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



linois, Indiana and Kentucky is not much inferior in dimensions to 

 the whole of England, and consists of horizontal strata, with nume- 

 rous rich seams of bituminous coal. Another carboniferous depo- 

 sit, 170 miles by 100, lies farther to the north, between Lakes Mi- 

 chigan and Huron. I may give the following as an example of the 

 almost boundless resources of fuel which this country affords. At 

 Brownsville, on the Ohio, there is a seam ten feet thick of good bi- 

 tuminous coal, commonly called the Pittsburg seam, which may be 

 followed the whole way to Pittsburg, fifty miles distant. " The 

 boundaries of this seam have been determined with considerable ac- 

 curacy by the Professors Rogers in Pennsylvania, Virginia and Ohio, 

 and they have found the elliptical area vthich it occupies to be 225 

 miles in its longest diameter, while its maximum breadth is about 

 100 miles, giving a superficial extent of about 14,000 square miles." 

 Mr. Lyell states that at Blossberg in Pennsylvania he was much 

 struck with the surprising analogy of the coal-measures to those of 

 Europe in mineral and fossil characters. The same grits or sand- 

 stones are found as those used for building near Edinburgh and New- 

 castle ; similar black shales occur, often bituminous, with the leaves 

 of ferns spread out as in a herbarium, the species being for the most 

 part identical with British fossil plants ; there are seams of good bi- 

 tuminous coal, some a few inches, others several yards in thickness 

 associated with beds and nodules of clay ironstone ; and the whole 

 series rests on a coarse grit and conglomerate containing quartz peb- 

 bles, very like our millstone grit. The same similarity of mineral 

 iand fossil characters to European coal-measures is found to prevail 

 throughout North America. That remarkable circumstance of the 

 very general occurrence of a sandy clay abounding in Stigmariae be- 

 neath the seams of coal, observed in the Welsh and other coal-fields 

 of Britain, is also found to prevail in those of North America. Mr. 

 Lyell saw numerous instances of this ; thus, at Pottsville in Pennsyl- 

 vania, there are thirteen seams of anthracitic coal (true bituminous 

 coal supposed to be altered by metamorphic action, a subject to which 

 1 shall allude hereafter), several of them from eight to ten feet thick, 

 and in a vertical position : on the side which had been the roof of the 

 coal, consisting of shales, he observed numerous ferns with stems of 

 Sigillaria, Lepidodendron and Calamites ; on the other side, that 

 which had once been the floor, he found an underclay with numerous 

 Stigmariae, often several yards, and even in some cases as much as 

 thirty feet long, with their leaves or rootlets attached. 



Theories of the Formation of Coal. 



It is scarcely possible to visit a coal-field, or to read the descrip- 

 tion of one, without being led to theorize on its mode of formation. 

 The origin of coal has long been a subject of great difficulty, nor 



loosa, to be no less than ninety miles long from north-east to south-west, with a 

 breadth of from thirty to forty miles. These coal-fields are portions of the great 

 Appalachian coal-field, with the same mineral and palseontological characters. 

 Mr. LyeU promises a more detailed account of his observationSi — April 3, 1846. 



