ATTENDING THE FORMATION OF COAL, &c. 261 



There can be no doubt, that the minute quantity of 

 carbonic acid present, had been formed by the atmospheric 

 oxygen, the large excess of nitrogen showing that the air 

 had been robbed of its oxygen ; whilst it is further evident, 

 that the coal itself was pouring out from its own materials 

 pure carburetted hydrogen. As light carburetted hydrogen 

 contains 2 atoms of hydrogen to.l atom of carbon; it is 

 also evident, that our present beds of coal are hastening to 

 the condition of anthracite, which consists almost entirely 

 of carbon, and has gone through all tbe stages of forest, 

 peat, and wood coal, to anthracite. Cannel appears to 

 differ from coal in having been formed under water; its abun- 

 dant remains of fish, interspersed through its substance, its 

 layere of sulphate of lime, which it could have obtained 

 from no other source, and which are not found in coal, all 

 prove this ; whilst its conchoidal fracture and homogeneous 

 texture, seem to indicate that it formerly existed in a softened 

 muddy state. Where the temperature has been low, we have 

 no evidence of the formation of any higher carburets of 

 hydrogen than that of fire-damp, which contains 1 atom of 

 carbon to 2 atoms of hydrogen, during the decomposition 

 which precedes the formation of coal ; but under an ele- 

 vated temperature, such as could be produced by an injec- 

 tion of ignited matter into the adjacent super or sub jacent 

 rocks, we have new affinities called forth, and compounds 

 formed, in which the relation of carbon and hydrogen is 

 altogether different, the atoms of carbon sometimes exceed- 

 ing those of hydrogen in the compounds, and sometimes 

 being of equal number. We know that no such injection 

 of heated matter now takes place within the limits of the 

 Lancashire coal-field, or the coal-fields of Northumber- 

 land and Durham ; and in the fire-damp of the mines sunk 

 there, we find no higher carburet of hydrogen than that 

 so often spoken of. But where the coal-measures have 

 been traversed by dykes of trap rock, which must have been 



