INTO BROWN OR WOOD- COAL. 351 



sides of the spring with sandstone, and the consequence was, that 

 all the outlets to the carbonic acid were closed, for this gas 

 generally gains access to the water from the sides of the spring. 

 From that time to the present this valuable mineral water has 

 disappeared, and in its place is found a spring of common 

 water. 



Springs of water impregnated with carbonic acid occur at 

 Schwalheim, at a very short distance from the layers of wood-coal 

 at Dorheim. M. Wilhelmi observed some time since, that they 

 are formed of common spring water, which ascends from below, 

 and of carbonic acid, which issues from the sides of the spring. 

 The same fact has been shown to be the case in the famed 

 Fachinger spring, by M. Schapper. 



The carbonic acid gas from the springs in the Eifel is, accord- 

 ing to BischofF. seldom mixed with nitrogen or oxygen, and is 

 probably produced in a manner similar to that just described. 

 At any rate, the air does not appear to take any part in the 

 formation of these acidulous springs. Their carbonic acid has 

 evidently not been formed either by a combustion at high or low 

 temperatures ; for if it were so the gas resulting from the com- 

 bustion would necessarily be mixed with f of nitrogen, but it 

 does not contain a trace of this element. The bubbles of gas 

 which escape from these springs are absorbed by caustic potash, 

 with the exception of a residuum too small to be appreciated. 



The wood-coal of Dorheim and Salzhausen must have been 

 formed in the same way as that of the neighboring village 

 of Laubach ; and since the latter contains the exact elements of 

 woody fibre, minus a certain quantity of carbonic acid, its com- 

 position indicates very plainly the manner in which it has been 

 produced. 



The coal of the upper bed is subjected to ar incessant decay 

 by the action of the air, by means 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 



