PRODUCTION OF WOOD-COAL. 321 



The wood coal which forms extensive layers 

 in the Wetterau (a district in Hesse Darmstadt.) 

 is distinguished from that found in other places, by 

 possessing the structure of wood unchanged, and by 

 containing no bituminous matter. This coal was 

 subjected to analysis, a piece being selected upon 

 which the annual circle could be counted. It was 

 obtained from the vicinity of Laubach ; 100 parts 

 contained 



Carbon . -. 57-28 



Hydrogen . . 6*03 



Oxygen . . 36'10 



Ashes . . 0-59 



10000 



The large amount of carbon, and small quan- 

 tity of oxygen, constitute the most obvious differ- 

 ence between this analysis and that of wood. 

 It is evident that the w^od which has undergone 

 the change into coal must have parted with a 

 certain portion of its oxygen. The proportion of 

 these numbers are expressed by the formula C33 

 H21 016. (The calculation gives 57*5 carbon and 

 5'98 hydrogen.) 



When these numbers are compared with those 

 obtained by the analysis of oak, it would appear 

 that the brown coal was produced from woody 

 fibre by the separation of one equivalent of hydro- 

 gen, and the elements of three equivalents of car- 

 bonic acid. 



