250 M. Bischof cm the Subterranean Course of Water, 



which exceeds the mean temperature of the earth's surface by 

 aibout 11° or 12° R., the carbonic acid cannot at that place be li- 

 quid. As it appears from the experiments of Davy and Fara- 

 day that carbonic acid is condensed at a temperature of — 8° R. 

 by 20 atmospheres, at 0° R. by 36, and at 5.6 R. by 40,* it re- 

 sults, that the increase of temperature of carbonic acid gas by 

 1° R. requires an increase of pressure of about 1^ atmospheres. 

 Now as, according to the observations hitherto made, the in- 

 crease of temperature towards the interior of the earth is about 

 1° R. for 96 feet, in round numbers, it follows that this depth, 

 considered as a column of water, is about equal to the pressure 

 of 3 atmospheres ; and thus, the increase of the hydrostatic pres- 

 sure is much greater in proportion than the pressure required 

 for the condensation of carbonic acid gas by the increase of tem- 

 perature. According to these suppositions, the hydrostatic pres- 

 sure will always, at a certain depth, overcome the increased ex- 

 pansive power which the carbonic acid gas has acquired from the 

 increase of temperature, and tlierefore, at such a depth, the car- 

 bonic acid can exist only in a liquid condition. Water which 

 mixes with liquid carbonic acid will receive a heat exceeding the 

 mean temperature of the place by at least 11° or 12° R. Since, 

 however, by much the larger proportion of acidulous springs 

 exceed the temperature of the place by only a few degrees, 

 such springs cannot have been produced by mixture rvith liquid 

 carbonic acid. 



There is, however, here a case to be excepted, when warm 

 springs, during their passag-e from beneath, become mixed with 

 cold springs, so as to have their temperature reduced. It can- 

 not be doubted, that, by means of at least a year's continued ob- 

 servations, such a case can be ascertained. The greater the 

 depth whence the springs arise, the more constant is the tempe- 

 rature, and the greater the supply of water. When such springs, 

 during their progress towards the surface, become mixed with 

 others which are variable in their temperature and in the quan- 

 tity of water, the mixture acquires the same characters. So far, 

 however, as my observations extend, it appears, that springs 

 having a temperature which exceeds the mean of the crust of 



• li. Gmelin's " Haridb. der Theor. Chemie," 3d edition, p. 124. 



