ANNALS 



OF 



PHILOSOPHY. 



AUGUST, 1819. 



Article I. 



Experiments to determine the Composition of the different Species 

 of Pit-Coal. By Thomas Thomson, M.D. F.R.S. 



X HE great difference which exists between the qualities of the 

 various species of pit-coal which abound in Great Britain must 

 have struck the most careless observer. These differences have 

 been long known to the consumers, and have led to the prefer- 

 ence or almost exclusive use of particular species for particular 

 purposes. It occurred to me last winter that a more accurate 

 determination of the constituents of our different kinds of coal 

 than had hitherto been made was likely to throw considerable 

 light upon their application to specific purposes, particularly the 

 manufacture of coke and the preparation of coal gas. It is 

 already known that some kinds of coal yield a much greater 



faseous product, and of a much better quality than others, 

 his I thought likely to depend upon specific differences in the 

 composition of the coal, and the following experiments will show 

 that the conjecture was well founded. 



The Wernerian arrangement of black coal into six subspecies, 

 though sufficiently minute, if not too much so, does not seem to 

 me to be applicable to the different kinds of coal which exist in 

 such abundance in Great Britain ; at least I have never been 

 able to arrange our British coals under it, far less to make it 

 subservient to point out the different qualities of coal as an 

 article of fuel, It will be necessary, therefore, in order that the 

 following experiments be understood, to employ here a new sub- 

 division of the various kinds of black coal. Those which I 

 examined are the coals which occur in the neighbourhood of 

 Vol. XIV. N° II, F 



