252 M. Bischof on the Subterranean Course of Water, 



or triple the amount of volume. In the interior of the earth 

 the absorption must, doubtless, under the continually increasing 

 pressure of water, amount to a much greater volume. When, 

 However, water impregnated by carbonic acid gas under such 

 high pressure gradually approaches the surface, a part of the 

 gas is separated from it, and makes its appearance in more or 

 less considerable streams. Berthier * is of opinion that this dis- 

 engagement of gas (in most of the hot mineral waters that con- 

 tain gas) is derived chiefly from a stream of carbonic acid gas, 

 which is produced simultaneously with the mineral water, and 

 which is much too considerable to be absorbed by the water ; 

 and he even thinks it extremely probable that it is only by the 

 influence of the pressure exerted by the carbonic acid gas gene- 

 rated in the subterranean laboratories that the water is brought 

 to the surface. Although this opinion formerly seemed to me a 

 probable one-f-, yet, now since I have had opportunities of making 

 observations on the gases evolved from mineral waters, I cannot 

 admit unconditionally its correctness. I believe, at least, that 

 streams of gas which merely accompany the springs, and are in- 

 dependent of them, are rare. Whether this case occurs or not 

 depends on the relative proportions of water and gas, on the 

 amount of the pressure of water, and on the temperature of the 

 water. The greater the quantity of water in proportion to the 

 gas which is evolved from the interior of the earth, and the 

 higher the column of water which exercises the pressure, and 

 the colder the water, so much the more easily is the gas absorbed. 

 Hence it is, when the gas meets the water in the lowest part of 

 its hydrostatic course, and when the canals of water proceed 

 downwards to a great depth in the earth, that the various rela- 

 tions are favourable for the entire absorption of the gas. When, 

 on the other hand, the gas enters the canals of water nearer the 

 surface of the earth, it may easily happen that only part shall 

 be absorbed, while the larger proportion passes freely through 

 the water. Since, in the interior of the earth, the temperature 

 of the earth increases with the hydrostatic pi'essure, the power 

 which water has of absorbing carbonic acid gas diminishes with 



• Annal. de Chim. et de Phys. t. xix. p. 27- 



■\ Die Vulkanischen Mineralquellen Deutschlands und Frankreichs, &c. 

 p. 215. 



