350 CONVERSION OF WOOD 



The formation of both these specimens of wood-coal appears 

 from these formulae to have taken place under circumstances 

 which did not entirely exclude the action of the air, and conse- 

 quent oxidation and removal of a certain quantity of hydrogen. 

 Now the Laubacher coal is covered with a layer of basalt, and 

 the coal of Ringkuhl was taken from the lowest seam of layers, 

 which possess a thickness of from 90 to 120 feet ; so that both 

 may be considered as well protected from the air. 



During the formation of brown coal, therefore, the elements of 

 carbonic acid have been separated from the wood either alone, 

 or at the same time with a certain quantity of water. It is quite 

 possible that the difference in the process of decomposition may 

 depend upon the high temperature and pressure under which the 

 decomposition took place. At least, a piece of wood assumed the 

 character and appearance of Laubacher coal, after being kept 

 for several weeks in the boiler of a steam-engine, and had then a 

 very similar composition. The change in this case was effected 

 in water, at a temperature of from 334° to 352° F. (150° to 160° 

 C), and under a corresponding pressure. The ashes of the wood 

 amounted to 0*51 per cent.; a little less, therefore, than these of 

 the Laubacher coal ; but this must be ascribed to the peculiar 

 circumstances under which it was formed. The ashes of plants 

 examined by Berthier amounted always to much more than this. 



The peculiar process by which the decomposition of these 

 extinct vegetables has been efFected, namely, a disengagement 

 of carbonic acid from their substance, appears still to go on at 

 great depths in all the layers of wood- coal. At all events, it is 

 remarkable that springs impregnated with carbonic acid occur in 

 many places, in the country between the Meissner, in the electorate 

 of Hesse, and the Eifel, which are known to possess large layers 

 of wood-coal. These springs of mineral water are produced on 

 the spot at which they are found ; the springs of common water 

 meeting with carbonic acid during their ascent, and becoming 

 impregnated with it. 



In the vicinity of the layers of wood-coal at Salzhausen 

 (Hesse-Darmstadt), an excellent acidulous spring of this kind 

 existed a few years ago, and supplied all the inhabitants of that 

 district ; but it was considered advantageous to surround the 



