and on the Absorption of Gases by Water. 257 



same manner, the vapour cavern of Pyrmont (the gaseous ex- 

 halation from the hunter sandstone, which is 66 feet above the 

 level of the spring used for common purposes) may be merely 

 a stream of gas which flows from the course of the spring. 



It is easy to perceive that such gaseous exhalations from the 

 channels of springs which flow out at lower positions, can most 

 easily appear at higher points, if the mouth of the spring is in 

 the rivulet or stream itself, and if the water there is very deep ; 

 for, since none of the gaseous exhalations from mineral waters 

 observed by me in the volcanic Eifel, and in the vicinity of the 

 Laachersee, have much force, so that they could not overcome a 

 higher pressure than that of a three or five inch column of water, 

 it is evident that a mineral spring, rising in a rivulet or river se- 

 veral feet deep, can exhibit no disengagement of gas, but that 

 the gas separated during the course of the water will come to 

 the surface, where there is no water pressure to overcome ; 

 therefore, upon dry heights, after having penetrated through 

 fissures and splits of the rock, or loose soil ; and thus the ap- 

 pearance will be presented as if the gaseous spring were alto- 

 gether independent of the water spring. 



By observing the perpendicular ascent of gas-bubbles from 

 mineral springs, one is easily induced to believe that there is a 

 perpendicular direction from the greatest depth, where disen- 

 gagement of carbonic acid has its origin. That this can rarely 

 be the case, is proved by the internal structure of the earth, so 

 far as is made known by escarpments of rock, and by mining 

 operations ; for the fissures in rocks, which form the canals for 

 springs, proceed in very various directions from the interior to 

 the surface of the earth. During the fitting up of several mi- 

 neral sjjrings, having a considerable exhalation of gas, at which 

 I was present, and partly directed the work, I have several times 

 remarked that the water and gas canals often proceed in a near- 

 ly horizontal or in a shghtly inclined direction. A very rich 

 gaseous exhalation, whicli was lost during the quarrying of the 

 rock, was again found at a horizontal distance of a little more than 

 twenty feet. At another spot, a disengagement of carbonic acid, 

 in bubbles, was remarked in a small hollow, when the latter was 

 filled with rain-water ; but in a dry season the presence of the 

 gas could be recognised only by tlie smell, and the suffocated 



