PROCEEDINGS OF PROVINCIAL SOCIETIES. 299 



a larger quantity of earthy matter. Of the collieries in the west 

 and north-west of Shropshire, the most considerable are those of 

 Llwyn-y-maen, near Oswestry. There are also some mines of lim- 

 ited extent on the borders of Herefordshire ; and the Clee hills, near 

 Ludlow, contain on their sides two or three small detached basins. 

 The vegetable origin of coal is now clearly ascertained. The Dud- 

 ley strata are entirely composed of distinct layers of plants converted 

 into common bituminous coal. In the coal-fields of the north of 

 England, cryptogamic vegetables and coniferae abound in immense 

 numbers. 



The fossil plants at present ascertained in the coal strata are esti- 

 mated at about 500 species. 



The formation of this substance is still involved in uncertainty. 

 It is conceived as probable that the coal-fields indicate the chief lo- 

 calities of the exuberant primeval vegetation, which being over- 

 whelmed by a deluge, and buried in the valleys or friths and estu- 

 aries under an immense torrent of mingled earth and water, charged 

 with carbonaceous and mineral matters, would be subject to that 

 pressure, moisture, reclusion of air, and confined moderate warmth 

 requisite to produce their conversion into coal. To account for the 

 exuberance of primeval vegetation, we must remember that these 

 northern latitudes had the high temperature and moisture now found 

 only in tropical regions. 



Coal, though enumerated under nearly 70 denominations, may 

 properly be classed into three species. 1st. — The brown or wood 

 coal, which is of comparatively recent geological date, and is parti- 

 ally distributed, and in which the change from wood to coal is 

 clearly distinguishable in the still existing vegetable fibres. 2ndly. — 

 The black, or common pit coal, comprising the rich caking pit coal 

 of Newcastle and other districts, including Shropshire and Stafford- 

 shire. Carbon, varying from 50 to 60 or 70 per cent., constitutes 

 the chief ingredient. 3dly. — The glance coal, found on the Conti- 

 nent, the United States of America, and in small quantities in Shrop- 

 shire and Staffordshire. Of this, many articles of taste and orna- 

 ment are fabricated. 



Common pit coal, submitted to destructive distillation in an iron 

 retort, obviously yields carburetted hydrogen, an aqueous ammoni- 

 acal liquor, and a thick fluid resembling tar ; chemical analysis, 

 however, resolves this substance into a greater number of elemen- 

 tary bodies, all of which are gases with the exception of the carbon. 

 The products above enumerated yield also several valuable articles 

 of commerce, and in consequence of immense quantities of pit coal 

 being distilled for the production of gas, the demand for the muri- 

 ate and carbonate of ammonia is principally supplied from this 

 source. Pure petroleum and limpid naptha are also obtained from 

 the same materials, and even the soot yields valuable ingredients, 

 to which it owes its efficacy as a manure. Thus, as Dr. Buckland 

 justly remarks, "from the wreck of forests that waved upon the 

 surface of the primeval lands, and the ferruginous mud that was 



