GEOLOGICAL SOCIETY OF LONDON. 



169 



notice of similar bones found in cutting the great drainage 

 canal of Mexico. The well sunk in pumiceous obsidean^ was 

 undertaken to procure better water than that which the dis- 

 trict afforded. The locality is the new inn between Perote 

 and Santa Gertrudes. In sinking the well to the depth of 

 sixty varas, ten were through sand and the debris of pumice, 

 and the remainder in pumice and scoriee, mixed with obsidian. 

 The volcanic rock then assumed a more compact character. 



March 2Sdf 1842. — R. J. Murchison, Esq., President, in 

 the chair : — 



I. — The Coal-fields of Pennsylvania and Nova Scotia. By 

 W, E. Logan, Esq., F.G.S. 



The observations detailed in this paper w^ere made during 

 the autumn of last year. The great carboniferous district of 

 Pennsylvania, which is only part of the vast area occupied 

 by similar deposits, and extending into the state of Mary- 

 land, Virginia, and Ohio, consists of numerous alternations 

 of grits, sandstones, argillaceous and carboniferous shales, 

 valuable bands of limestone and seams of coal, in some dis- 

 tricts bituminous, and in others anthracitic. Beneath this 

 series occurs a very hard, coarse, quartzose conglomerate, 

 which, in the south-western portions of the coal district, is 

 from 800 to 1200 hundred feet thick; but which in the north- 

 west thins out considerably. Under this conglomerate is a 

 red shale, also of variable importance, being 3000 feet thick 

 in the south-east portions of the state, less than 100 in the 

 western, and disappearing in the north-west. In its lower 

 part it contains a partial bed of fossiliferous limestone. To 

 the red shale succeeds a formation composed of white, grey, 

 and buff-coloured sandstones and conglomerates, occasionally 

 interstratified with beds of shale, and it is, apparently of uni- 

 form thickness. The v/hole of these deposits are conform- 

 able to each other, and are considered as belonging to the 



