M. Bischof o?i the Subterranean Course of Water, 4-c. 247 

 ticularly in limestone and qiiadersandstone mountains, and ge- 

 nerally in those formations in which fissures abound. Thus, 

 for example, in the chalk hills of the Westphahan flcetz forma- 

 tion, springs occur which are in reality subterranean rivers, such 

 as the springs of the Jordan, the Lippp, the Pader,* &c. 



2. The water of the atmosphere penetrates by clefts to a 

 greater or less depth in the interior of the earth, fills all the 

 clefts connected with those by which it entered, reascends by 

 them according to the laws of hydrostatics, and comes to the 

 surface as springs at one or several points which are at a some- 

 what lower level than the spot where it commenced its course. 



This case can only occur when all the communicating fissures 

 are, like hydraulic pipes, entirely filled with water. The water, 

 however, may flow for some time in open canals, as in the pre- 

 ceding case, before it reaches the close fissures. The pressure 

 of the height will only begin to exert its influence from that 

 point. Until then, the water comes in contact with atmos- 

 pherical air, and absorbs it. For example, the following case 

 may occur. The water flows from a to /a 



b, in an open canal, and from 6 to c in /i^-^^J^ 



an inclosed channel, which at c becomes ^ f""" (^ 



enlarged, and at / contains almosphe- \\ jr-^ 

 ric air. On account of the pressure tt / 

 exerted by b c, the water absorbs a \J 

 larger portion of atmospheric air than it A 

 can under the ordinary pressure of the atmosphere; it then 

 flows in close canals to d, ascends again to e, and there flows 

 out as a spring. Under such circumstances, we can under- 

 stand that the water allows the air it had absorbed under the 

 pressure of the water b c gradually to escape as it approaches 

 its outlet, and the water, when it flows out, will retain only 

 so much air as it can under the usual pressure of the at'^ 

 mosphere. This is the cause of the frequent occurrence of 

 a disengagement of gas at e in springs in limestone moun- 

 tains. Several gaseous exhalations of a similar nature, which 

 I have had an opportunity of examining, afforded a sniall- 

 • Compare my paper in the new " Jahrbuch der Chemie und Phys." 

 1833, Part xiiL p. 272. 



