376 Prof. Bischof on the Natural History of 



supply their place. We may easily explain this by the ab- 

 sence of rocks containing alkalies ; for instance, basalt or any 

 other volcanic rocks. The clefts produced by these fractures 

 reach certainly to great depths ; carbonic acid gas may be 

 evolved from them, but its elasticity seems to prevent the pene- 

 tration of meteoric water. The mean temperature of th^' 

 mineral springs there, exceeds, therefore, but little that of the 

 place of their occurrence. This is especially the case with the 

 mineral springs at Meinberg; whose considerable annual varia- 

 tions of temperature prove that they take their origin very 

 near the surface. The considerable elasticity with which the 

 carbonic acid gas escapes, and which is greater than I have ob- 

 served at any place where gas is evolved, prevents, no doubt, 

 the deep penetration of meteoric water. Moreover, we may 

 remark, that the inclination of the strata, from the centre 

 downwards in every direction, carries the meteoric water away 

 from the seat of the evolution of the carbonic acid gas. Even 

 supposing, then, that the water could penetrate to the depth of 

 the channels of carbonic acid, it would not rise, owing to the 

 absence of the pressure of a column of water. The section of 

 the valley of elevation of Fyrmont, taken from Hoffmann's 

 work. Fig. 3. distinctly shews the inclination of the strata a &, 



Fig. 3. 



^^9 ^f^S^ ^^9 ^^5 from the centre downwards. 



It is possible that the raising and fracture of the secondary 

 strata in such valleys of elevation, was the consequence of the 

 elevation of volcanic masses from beneath, which masses have 

 not appeared at the surface. Supposing this to be the case, we 

 can easily imagine that at such places mineral springs may be 

 produced which contain carbonates of alkalies, because the mete- 

 oric water only can penetrate to these masses. But the low tem- 

 perature of the acidulous springs in question, shews that me- 

 teoric water penetrates to \ery small depths only at these 

 places. 



