81 
" coal and culm or bituminous and common coal. They 
" are in fact mere mineral varieties of the same sub- 
" stance which occur in formations accumulated at 
"the same period."* Sir C. Lyell, in his Manual, 
p. 333, quoting Liebeg and BischofF, says, " The disengage- 
" ment of all the gases gradually transforms ordinary or 
" bituminous coal into anthracite ; to which the various 
" names of splint, glance, culm, and many others have been 
" given." Liebeg, in his Chemistry, gives the following 
analysis of Mineral coal : " Hydrogen 13, carbon 24," and 
states that it " appears to be produced by long-continued de- 
" composition of wood or wood coal, by which carbonic 
" acid and water, and carburetted hydrogen are separated ; 
" when the whole of the hydrogen is removed in the form 
" of carburetted hydrogen the residue must be anthracite, 
" which is nearly pure carbon." Professor Johnston, in his 
inaugural address to this Society, said " Cannel coal con- 
" tained one atom more water than cokeing coal," which is 
very correct. Dr. A. A. Hayes, United States, in a paper 
read at the Dublin Meeting of the British Association, 
in 1857, has evidently been struck forcibly with the difficulty 
to account for the conversion of bituminous coal into anthra- 
cite. No coal tar being found in the vicinity of the beds, 
how is the absence of this material to be accounted for but by 
supposing that it has been originally a different kind of deposit ? 
Dr. Hayes details a course of experiments to illustrate his 
opinions, but the experiments were performed under a light 
atmosphere of gases, whereas the bituminous coal has an 
enormous weight of superincumbent strata. This, to me, 
appears a fatal objection to his experiments in proving the 
change of the coal after being deposited, as there should be 
springs of natural bitumen or petroleum near the cannel 
beds, if this theory be true. 
* Silurian System, vol. 1, p. 371. 
F 
