58 Natural History of Volcanos and Earthquakes. 
strata, and extending from B to D, and if, lastly, the new forma- 
tion contain impervious strata, then the conditions will undergo 
achange. The meteoric water, which penetrates at A, between 
each separate portion, will now all issue in the form of rising 
springs at B, between the elevated mountain and the new strat- 
ified formation which lies at its side. Should any obstacle here 
present itself to its exit, the water will even take a retrograde 
course B D, and issue at D, in which case the water between the 
last formed horizoutal stratum and the impervious stratum lying 
under the newest raised ones will unite with it. We will not, 
however, enter into farther particulars, as many circumstances 
may be supposed to exist which modify the course of the springs} 
and still more complicated relations naturally arise, when, after 
the deposition of the latest formed stratum, the elevation and 
raising are repeated. It will be sufficient to have called atten- 
tion to the circumstance, that rising springs can exist ouly when 
the originally horizontal position of the stratified formations 
has been destroyed by elevations; and that the most copious 
springs, and those which arise from the greatest depths are found 
precisely at the limits between the elevated masses and the raised 
strata. 
Numerous instances can be cited in proof of this assertion. 
The Pyrenées and Alps, present very characteristic cireumstan- 
ces. ‘Thus Pallasou* shows, that not only are the majority of the 
hot springs in the Pyrenées, situated in the great granitic district 
at the eastern side, but also, that all the others issue only from 
hollows of the newer formations, where the granite rises from 
beneath, at the foot of the declivities. He shows also, that evet 
the degree of temperature of these springs depends on the greater 
or less exposure of their source; for the thermal springs neater 
the principal granitic mass are warmer, while those more remote 
are colder. 
Professor Forbes has likewise pointed out, in an interesting 
memoir on the temperatures and geological relations of certail 
hot springs, particularly those of the Pyrenées,+ that, in the 
departments of the Arriége and the Pyrenées Orientales, whet 
granite formations preponderate, in almost every case which he 
| aris See 
* Mem. pour servir 4 I'Hist. Natur. des Pyrenées, 1815, p. 435, 459. 
t Philos. Transact. for 1836, p. 575 
