66 Natural History of Volcaiios and Earthquakes. 



could be pursued from ten to twenty feet in a horizontal direc- 

 tion, or nearly soj and which doubtless were prolonged still far- 

 ther,* 



If the carbonic acid gas arises from below with considerable 

 elasticity, and the cleft contracts very much from b to c, then it 

 may easily happen that the meteoric water may penetrate but 

 little below b. In this case, the column of water a i, will be as 

 it were supported by the column of gas,f and at the point of con- 

 tact- a constant absorption of the gas will be going on. In this 

 manner, probably, are those mineral springs formed, which 

 abound in carbonic acid gas, but contain very little solid matter, 

 and whose average temperature exceeds but little that of the 

 neighboring wells. It must frequently be the case, moreover, 

 that many spritigs which rise from a greater depth, and there- 

 fore are originally warm, become cooled by mixture with cooler 

 springs. 



The warmest of the mineral springs^in the environs of the 

 Laacher See exceed the mean temperature of the ground by 7 

 to 10^ Fahrenheit. What is worthy of remark is, that they rise 

 from the deepest spots of the valley, where, therefore^ their sub- 

 terraneous channels are proportionably deepest under the rock, 

 and possess already a relatively higher temperature. On pursuing 

 the mineral springs up the valley, we find that their temperature 

 decreases in a somewhat regular ratio. J 



The proportionably small number of clefts in the clay-slate 



may 



Eifel, and the Ti 



J 



that, in the 



siderable high temperature occur, though the channels of the car- 

 bonic acid gas lead down to such great depths, probably to points 



where a red heat exists. Such warm springs may perhaps owe 

 their existence to the favorable circumstance of a cleavage surface, 

 which intersects the strata at an obtuse angle, leading up from the 

 cleft between the volcanic cone and the clay-slate rock^ and open- 

 ing at a valley, as cd. Perhaps the warm springs at Bertrich 



* Neues Jahrbuch do Chem. et Phys. t. viii, p. 423, year 1833. 

 , \ The rising and falling of the periodic spring of the salt-work at Kissingrnjis 

 doubtless a consequence of the elasticity of carbonic acid gas. See PoggendorflPs 

 Ann. t xl,p. 495. 



t So in the chain of Taunus mountainSj the warm springs rise deep in the valley, 

 the cold acidulous springs on the heights. 



