INTO MINERAL COAL. 327 



Regnault, the composition of the combustible 

 materials in splint coal from Newcastle, and cannel 

 coal from Lancashire, is expressed by the formula 

 C24 H13 O. When this is com pared with the com- 

 position of woody fibre, it appears that these coals 

 are formed from its elements, by the removal 

 of a certain quantity of carburetted hydrogen 

 and carbonic acid in the form of combustible 

 oils. The composition of both of these coals is 

 obtained by the subtraction of 3 atoms of carbu- 

 retted hydrogen, 3 atoms of water, and 9 atoms of 

 carbonic acid from the formula of wood. 



C36 H22 O22=: wood 

 3 atoms of carburetted hydrogen C3 H6 



3 atoms of water . . H3 O3 

 9 atoms of carbonic acid C9 O18 



Mineral coal 



C12 H9 O21 



O24 H13 O 



Carburetted hydrogen generally accompanies all 

 mineral coal ; other varieties of coal contain volatile 

 oils which may be separated by distillation with 

 water. (Reichenbach.) The origin of naphtha is 

 owing to a similar process of decomposition. Cak- 

 ing coal from Caresfield, near Newcastle, contains 

 the elements of cannel coal, minus the consti- 

 tuents of olefiant gas C4 H4. 



The inflammable gases which stream out of clefts 

 in the strata of mineral coal, or in rocks of the coal 

 formations, always contain carbonic acid, according 

 to a recent examination by Bischojf, and also car- 

 buretted hydrogen, nitrogen, and olefiant gas ; the 



