Volcanos and Earthquakes, 373 



spots (which are constantly met with in the vicinity of the 

 brooks, and consist of little basins filled with water) to be 

 actual mineral springs. If, however, the basin be emptied out, 

 or the water drained off, it is at once perceived that no water 

 springs up, but that merely an escape of gas takes place. I 

 have had an opportunity of causing such gas-springs to be en- 

 closed, and found the disengagement of carbonic acid gas to 

 be extremely copious.* Fissures, covered by accumulated 

 eartli, are very frequently met with. If such a place presents 

 a slight excavation, in which the gas collects, suffocated animals, 

 as birds, mice, frogs, &c., are commonly found in it. 



As springs run in the most different directions between the 

 surfaces of strata, and through the fissures of the strata, so al- 

 so do these disengaged gases. I have often had occasion to 

 cause excavations to be made, in places where a scanty vegeta- 

 tion rendered the disengagement of carbonic acid gas at some 

 depth probable. Fissures were often met with in the trass, out 

 of which rose abundant streams of this gas. Sometimes natu- 

 ral canals in the trass were found under a covering of SphdrO' 

 siderit, wliich could be pursued from ten to twenty feet in a 

 horizontal direction, or nearly so, and which doubtless were 

 prolonged still farther.-f* 



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 b, will 

 be as it were supported by the column of gas,J and at the 

 point of contact, a constant absorption of the gas will be going 

 on. In this manner, probably, are those mineral springs form- 

 ed, which abound in carbonic acid gas, but contain very little 

 solid matter, and whose average temperature exceeds but little 

 that of the neighbouring wells. It must frequently be the 

 case, moreover, that many springs which rise from a greater 



* Jahrb. der Chemie et Phys. t. hi. p. 129. (1029.) 

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

 Ij: The rising and falling of the periodic sprirg of the salt- work at Ki»- 

 vjerij is doubtless a consequence of the elasticity of carbolic acid gas. See 

 ^oggendorff's Ann. t. xl. p. 49c. 



m^i 



