io6 Aluminous TFood, Bovey Csal^ IS-l^ 



SECT. IV. 

 'WHEN we confider the fads which apparently prove that vegetables have contributed 

 -principally to the formation of bitumen, we have every -reafon to expe£t that mixtures of 

 vegetable matter with bitumen fliould frequently occur. But by the mixture of bitumea 

 with the parts of vegetables, we underftand the remains and parts of vegetables mixed and 

 >.Conne£tcd with tiie bitumen which they themfelves have produced. 

 ■This fecms to be the nature of the fubftance called 



-BITUMINOUS WOOD, as well as of TURF and PEAT. 

 "Bituminous or foffil wood is found in many places ; but in refpect to that which is found 

 atBovey, near Exeter, and which is therefore called Bovey coal, there are forae peculiarities 

 which deferve to he mentioned. The Bovey coal is a darlc brown, light, brittle fubftance, 



Avhich in texture and other external properties much refembles wood which has been half 



• charred. 3t is not found as fcattered lags or trunks, but forms regular flrata. 



The pits are on a heath which is flat and fandy ; the ftratum of fand is however but thin, 

 after which a pale brownifli grey clay is found mixed with quartz pebbles. This prevails to 

 about fix feet, at which depth the firft flratum of the coal commences. The quality of this 

 is however much inferior to that of the fubfequent ftrata, which in all amount to feventeen, 



-producing a depth of nearly feventy-four feet from the furface. Between each ftratum of 

 coal is a ftratum of clay. The diredion of the ftrata is from eaft to weft, and the inclina- 

 tion or dip is from north to fouth. The inferior ftrata arc thought to afford the beft coal, 

 and the coalis more folid and of a better quality towards the fouth. The thickeft ftratum 



•of coal is from fix to eight feet*. 



The Bovey coal burns readily with a flame like half-charred wood : it does not crackle, 



.:and, if but moderately burned, forms charcoal ; or if completely burned, it leaves a fmall 

 quantity of white afties exaflly fimilar to thofe of wood. The fmell of it when burning alfo 

 refembles that of wood, with a faint difagreeable odour. It is certainly very remarkable 

 that this fubftance (h&uld form regular ftrata, although it poffeiTes the texture and moft of the 

 properties of wood ; and that thefe ftrata do not exhibit any of thofe irregularities on their 

 furfaces, which might be expelled, on the fuppofition that they were formed by the roots, 

 trunks, and branches of trees long buried in the earth. It is alfo difficult to imagine wood 

 to have been tranfported and depofited in this place at feventeen different periods, and yet 

 it muft be allowed that thefe ftrata have been formed by fucceffive operations. I muft con- 

 fefs, that after having twice vifited and examined the fpot exprefsly for the purpofe, I ftill 

 find myfelf utterly unable to offer any opinion upon the fubjeft. 



The charafters of bitumen are but little apparent in the Bovey coal, and the fuperior 

 (Irata even appear to have loft a portion of their combuftible principle, while the inferior 

 ftrata poffefs it. The lower parts alfo of thefe ftrata are more compadt and more combuftible 

 than thofe parts which are immediately upon themj-. 



Another 



• In the winter, twelve men can raife about no tons of tills coal in a week, the whole of which is employed 

 in a neighbouring pottery. 



f At about 100 yards to the weft of the pits, is a bog of confiderablc extent, where peat is cut, and decayed 

 iceets and trunks of trees are found, which do not, however, in the leaft approach to the nature of the Bovey 



•coal. 



