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dom, as Lord Dundonald has difcovered and abundantly proved |, 

 and alfo of that chared refiduum called Coak, the only one that 

 can be reforted to in many cafes, and in moft fupcrior to vege- 

 table charcoal. 



Coals and bitumens are however fubftances that refift the 

 ufual modes of analyfis ; they elude the adion of aqueous, acid, 

 alkaline or fpirituous menftruums ; and diftillation, the only mode 

 hitherto ufed, confounds and varies their natural contents. 



Reflecting on thefe obftacles to an exadl difcrimination of 

 bitumens and coals, and of the various kinds of thefe laft, it 

 occurred to me that partly by combuftion, and partly by their 

 efficacy in decompofing nitre, the fecret of their internal compofition 

 might polTibly be unveiled. 



I ^. Combujlion. I have obferved that all the fpecies of foHd 

 bitumen, properly fo called, when laid on a red hot iron, burn 

 with a large bright flame, fm©ke and foot, leaving none or fcarce 

 any coaly refiduum, and only a little afhes. 



That the fofter bitumens, as maltha, burn in the fame man- 

 ner, leaving no coal, but only a little afhes, and requiring no 



increafe of heat for their intire confumption. 



That 



f Upon the moft minute enquiry why coal varnifli is not more commonly employed 

 in paying the bottoms of fhlps, I have been informed the principal reafon is, that it 

 fucceeds too ivtU — The fhips not requiring fuch frequent repair. 



