PEAT. 355 



a bistre may possibly have been first produced by heat, 

 and then converted into coal, or asphaltum, through 

 water ; since the vegetable resins are thus bituminized, 

 without even loss of form ; partially in the retinasphal- 

 tum of Bovey and Highgate, and perfectly in the case 

 of amber : the former, especially, illustrating the gra- 

 dual action of water in the cases of peat and lignite. 



Trusting that the chemical nature of this process, 

 and of all these substances, is now at length intelli- 

 gible, I may proceed to what remains respecting coal ; 

 using that term, as I have the word lignite, in its mi- 

 neralogical sense. If Kirwan, equal, on this subject, 

 in his chemistry and his geology, determined that coal 

 was a compound of bitumen and charcoal, I need not 

 point out the puerility of his experiments, and scarcely 

 indeed the ignorance of his phraseology. Charcoal 

 itself is not a simple substance, but bitumen is as 

 compound a one as coal ; every one of these inflam- 

 mables consisting of the same elements, if in different 

 proportions : so that we may even conceive a series 

 beginning with carbon and ending in hydrogen, while 

 the actual one ranges from naphtha to anthracite. 

 Though chemistry must take more accurate views, 

 knowing that other elements enter into the bitumens, 

 this general one is sufficient for the present purpose. 



The different kinds of coal form a series, graduating 

 from the bitumens, and commencing, as nearly as is 

 well possible, where asphaltum stops. Cannel coal, 

 the most inflammable and volatile, stands first; fol- 

 lowed by the less bituminous " parrot" coal of Scot- 

 land, successively by the " fat coals," through the se- 

 veral varieties that are distinguished by their different 

 dispositions to " cake," and then by the dry ones, such 

 as Welsh culm and Kilkenny coal ; while the series 

 terminates in anthracite, approaching to charcoal, yet 



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