70 = Natural History of Volcanos and Earthquakes. 
_ where, in consequence, the penetration of meteoric water into 
the interior of our earth has been rendered possible, and where 
natural hydraulic tubes have been formed by the upraising of 
strata, there the phenomena of thermal and mineral springs were 
the consequence. 
We should transgress our limits, were we here to pursue the 
subject of thermal springs in their chemical relations, since the 
general aim of these remarks is to show that their degree of heat 
depends on the greater or less depth of their origin, consequently 
wholly and solely on central heat. The following remarks, how- 
ever, upon their chemical constitution, may perhaps not be en- 
tirely 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. e following 
conjecture is probable. If considerable quantities of carbonic- 
acid gas are disengaged from the interior, which are absorbed 
under strong hydrostatic pressure by the water, and thus act on 
the voleanic stone, decompositions ensue. The alkalies 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 al- 
kalies, 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 voleanic matter, and more so from the 
_ Neptunian formations. In this matter probably, are formed the 
great number of springs, which rise in the neighborhood of basal- 
tic hills. Where there is no disengagement of carbonic acid gas 
from the interior, no such mineral springs are found; at least we 
cannot assume that in this case the volcanic rock contribtites any 
thing essential to the constituents of the springs. 'Thus, prob- 
ably, neither in the Pyrenées nor Alps do the springs take up any 
thing essential from these rocks. The circumstance, that springs 
of very various chemical composition arise in the vicinity of the 
granite of different mountains, might here serves as an indirect 
proof. At the same time, the nearly similar composition of 
the springs occurring in the neighborhood of the basaltic cones, 
where carbonic acid gas is disengaged, however different may 
