ERKMACAUSIS. 715 



on at great depths in all the strata of wood coal. The compo- 

 sition of the splint coal of Newcastle and cannel coal of Lan- 

 cashire being C 24 H 13 O, according to the analyses of both 

 Richardson and Regnault, mineral coal is obviously formed from 

 woody fibre in a different manner from brown coal. The com- 

 position of both splint and cannel coal is obtained by the subtrac- 

 tion of 3 atoms of carburetted hydrogen, 3 atoms of water, and 

 9 atoms of carbonic acid from the formula of wood (Liebig) : 



Three atoms of carburetted hydrogen. C 3 H 6 



Three atoms of water HsO 3 



Nine atoms of carbonic acid. . C 9 O 18 



Co fi H 00 O 00 wood. 



362222 



Mineral coal. 



Caking coal from Caresfield, near Newcastle, is C 20 H 9 O, or 

 contains the elements of cannel coal, minus the constituents of 

 olefiant ga's C 4 H 4 (Liebig). The inflammable gas of coal mines 

 is principally light carburetted hydrogen, but it has been 

 observed by Bischoff occasionally accompanied by notable quan- 

 tities of olefiant gas. Such decompositions, however, are not 

 due to eremacausis, and indeed take place in materials covered 

 by such a mass of strata as must entirely exclude air, but are 

 more analogous to the internal reactions observed in organic 

 matters, and known as species of fermentation, in which the 

 elements of a compound substance (such as sugar) divide 

 themselves into two or more groups, without the incorporation 

 of any extraneous element, except perhaps the constituents 

 of water. 



The absorption of oxygen by alcohol in its acetification is a 

 true eremacausis, so also is the process of nitrification. Oxi- 

 dation is promoted in many organic bodies by contact with an 

 alkali ; thus alcohol holding potash in solution soon becomes 

 brown from oxidation, and a resinous matter appears with 

 all the products of the decomposition of aldehyde. The 

 oxidation of gallic acid, hematin and many other compounds is 

 promoted by the same influence ; many vegetable substances 

 exhibit a rapid absorption of oxygen on the addition to them of 

 ammonia, and form splendid violet or red coloured liquids, such 

 as the colouring principles of the lichens. On the other hand, 



