270 On certain Products obtained 



philosophers of high reputation have supposed that fire has been 

 a probable cause of this conversion, and that this theory is sup- 

 ported liy considerable evidence in some analogous cases, it is 

 our duty to examine by experiment, what effects conducing to 

 this end may result from our limited trials. The foregoing ex- 

 periments show that the fire of our furnaces does not convert 

 wood into bitumen, and the processes of Nature seem to prove 

 that water can produce this effect, and that jet, the bituminous 

 lignite whicli approaches nearest to coal in its chemical cha- 

 racters, is the result of this action. Y'et there is an interval 

 between jet and coal, as I have already observed, requiring ex- 

 planation. The chemical characters nuiy be identical, l)ut the 

 mineralogical resemblance is still wanting. It is possible that 

 the agency of fire may account for this ultimate change, and 

 that its action on beds of lignite and peat has converted not 

 wood but vegetable matter already bituminizcd by water into 

 coal. Pursuing this train of investigations I was induced to 

 try if jet, the most perfectly bituminized lignite, could by the 

 application of heat inider pressure be conveited into coal. For 

 this purpose I introduced powdered jet into gun barrels, placing 

 it between two portions of rammed Stourbridge clay, with the 

 view of absori)iug a part of the distilled petroleum when it might 

 be formed in greater quantity than was requisite for the success 

 of the experiment, and where by its conversion into hydrogen it 

 might endanger the bursting of the apparatus. The barrels, 

 which were Swedish, were held in a moderate red heat till they 

 burst, when they were instantly withdrawn and cooled in water 

 to prevent the further volatilization of the bitvnninous matter. 

 As the opening was generally no larger t!ian a pin hole, there 

 was no difficuky in cooling the apparatus in time. In this way, 

 ^mong some failures, I procured a perfect fusion of the jet, which 

 exhibited t!ie true characters of coal, and was taken out with 

 the impression of the irregularities, in the barrel. I need not 

 add that in this case the produce had not merely the colour and 

 inllainmability but the fracture of coal and its odour on burning. 

 It is not unlikely that by a sufficient repetition of these experi- 

 meutcj with better regulated heats and more leisure than I pos- 

 .sesscd, several varieties of coal might have been in this way pro- 

 duced. Indeed some' of the specimens exhil)ited a dry, and 

 others a fat appearance, but it was impossible in general to de- 

 tach them from the barrels without reducing them to small frag- 

 ments. Two other circumstances occurred deserving of notice. 

 In one or two cases where the heat had been too great, a portion 

 of the jet was reduced to charcoal, which continued attached to 

 the coaly matter, and the clay was in every instance blackened 

 to a co!}sidcrable distance from the jet, and converted into a 



hard 



