378 Prof. Bischof on the Natural History of 



general aim of these remarks is to shew that their degree of 

 heat depends on the greater or less depth of their origin, con- 

 sequently wholly and solely on central heat. The following 

 remarks, however, upon their chemical constitution, may per- 

 haps not be entirely superfluous. 



The chemical ingredients of those springs which take their 

 origin at the boundary between volcanic and Neptunian forma- 

 tions, are derived in some springs from the former, in others 

 from the latter formations, in others again from both. The 

 following conjecture is probable. If considerable quantities of 

 carbonate acid gas are disengaged from the interior, which are 

 absorbed under strong hydrostatic pressure by the water, and 

 thus act on the volcanic stone, decompositions ensue. The al- 

 kalies which are found in all stony masses of igneous origin, are 

 extracted by the carbonic acid, and taken up by the water as 

 carbonate of alkalies, and especially carbonate of soda. In 

 the same manner are formed the bicarbonates of lime, magnesia, 

 and of protoxide of iron. Metallic chlorides and sulphates may 

 perhaps be less frequently derived from volcanic matter, and 

 more so from the Neptunian formations. In this manner pro- 

 bably are formed the great number of springs, which rise in 

 the neighbourhood of basaltic hills.. Where there is no disen- 

 gagement of carbonic acid gas from the interior, no such mi- 

 neral springs are found ; at least we cannot assume that in this 

 case the volcanic rock contributes any thing essential to the 

 constituents of the springs. Thus, probably, neither in the 

 Pyrenees nor Alps do the springs take up any thing essential 

 from these rocks. The circumstance, that springs of y^ry va- 

 rious chemical composition arise in the vicinity of the granite 

 of different mountains, might here serve as an indirect proof. 

 At the same time, the nearly similar composition of the springs 

 occurring in the neighbourhood of the basalt cones, where car- 

 bonic acid gas is disengaged, however different may be the 

 Neptunian formations, is an argument in favour of these springs 

 deriving their ingredients principally from the basalt. 



The organic matter found in such abundance in the sulphu- 

 reous springs of the Pyrenees (baregine, glairine, animal mat- 

 ter) proves, that their chemical constituents must be derived, 

 at least in part, from the Neptunian formations. Since no carbo- 



