326 CONVERSION OF WOOD 



of which its hydrogen is removed in the same 

 manner as in the decay of wood. This is recognised 

 by the way in which it burns, and by the formation 

 of carbonic acid in the mines. 



The gases which are formed in mines of wood- 

 coal, and cause danger in their working, are not 

 combustible or inflammable as in mines of mineral 

 coal ; but they consist generally of carbonic acid 

 gas, and are very seldom intermixed with combus- 

 tible gases. 



Wood-coal from the middle bed of the strata at 

 Ringkuhl gave on analysis 65*40 - 64'01 carbon 

 and 4*75 4*76 * hydrogen ; the proportion of 

 carbon here is the same as in specimens procured 

 from greater depths, but that of the hydrogen is 

 much less. 



Wood and mineral coal are always accompanied by 

 iron pyrites (sulphuret of iron) or zinc blende 

 (sulphuret of zinc); which minerals are still formed 

 from salts of sulphuric acid, with iron or zinc, 

 during the putrefaction of all vegetable matter. It 

 is possible that the oxygen of the sulphates in 

 the layers of wood-coal is the means by which the 

 removal of the hydrogen is effected, since wood- 

 coal contains less of this element than wood. 



According to the analysis of Richardson and 



* The analysis of brown coal from Ringkuhl, as well as all those of the 

 same substance given in this work, have been executed in this laboratory 

 by M. Kuhnert of Cassel. 



