68 Natural History of Volcanos and Earthquakes. 



valleys of elevation. The most remarkable of these, are those 

 of Pyrmont, Meinbe7^g, and Driburg, where the well-known 

 chalybeate springs rise, accompanied by a considerable disen- 

 gagement of carbonic acid gas. Pyrmont and Mmiherg lie 

 precisely at those places where the directions of the northeastern 

 system of mountains and of that of the Rhine intersect. 



Here, therefore, we find also a considerable disengagement of 

 carbonic acid gas ; yet no volcanic masses which have broken 

 through ; but only the secondary strata of shell limestone, of 

 keuper and variegated sandstone, raised up and fractured. The 

 mineral springs are of another kind, and the alkaline carbonates 

 are wanting, while sulphates and metallic chlorides supply their 

 place. We may easily explain this by the absence of rocks con- 

 taining 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 penetration of meteoric water. 

 The mean temperature of the 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 variations 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 observed at any place where gas is evolved, 

 prevents, no doubt, the deep penetration of meteoric water. More- 

 over, 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 



Fig. 3. 



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

 the valley of elevation of Pyrmont, taken from Hofi'mann's 

 work. Fig. 3, distinctly shows the inclination of the strata a 6, 

 ccZ, e/, g A, ik.^ 1 711, from the centre downwards. 



