412 



ATMOSPHERE OF CARBONIC ACID. 



[Ch. XVII. 



where the water is seen bubbling and boiling 1 up with much 

 noise, in consequence of the abundant disengagement of this 

 gas. In the environs of Pont- Gib and, not far from Clermont 

 a rock belonging to the gneiss formation, in which lead-mines 

 are worked, has been found to be quite saturated with car- 

 bonic acid gas, which is constantly disengaged. The car- 

 bonates of iron, lime, and manganese are so dissolved, that 

 the rock is rendered soft, and the quartz alone remains un- 

 attached.* Not far off is the small volcanic cone of Chaluzet, 

 which once broke up through the gneiss, and sent forth a 



lava-stream. 



Disengagement of free carbonic acid 



history of volcanos,t has shown what 



carbonic acid gas are inhaled in the vicinity of the extinct 



craters of the Rhine (in the neighbourhood of the Laacher- 



— Prof. Bischoff, in his 



■s 



of 



see, ioi 



springs 



exam 



Nass 



he Eifel,) and also in the mineral 

 other countries, where there are no 



immediate traces of volcanic action. It would be easy to 

 calculate in how short a period the solid carbon, thus emitted 

 from the interior of the earth in an invisible form, would 

 amount to a quantity as great as could be obtained from the 

 trees of a large forest, and how many thousand years would 



seam 



om 



the same source. I have already alluded to the 

 doctrine favoured by some geologists of the existence of an 

 atmosphere highly charged with carbonic acid, at the period 

 of the ancient coal-plants, and have endeavoured to show that 



t 



We have no rig 



mer 



chemical constitution of the 



estimatin 



ftxmic acid gras emitted from 



dead animal an 



5 



putrefaction, and comparing it with the volume of the same 

 gas annually extracted from the air, and afterwards stored 

 up in the earth's crust in the form of peat, buried timber, and 



o 



matter derived from the animal king 



* Ann. Scient. de l'Auvergne, tome ii. 1839. 

 June, 1829. 



j See Lyell's Travels in N. America 



) 



t Edinb. New Phil. Journ. Oct. June. 1829. 





C* 



f 



V 1 



trt* 



& 



c 



iece 



r 



from 

 In 



espe ( 

 beds 

 ock 



lime 



the 



bloc 



of* 



read 



T 

 ioh 



nat 



SHU 



eiia 

 in> 



of | 



ofi 



mii 



all 



p' 



g 



j 



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 1 



80 



