56 , Natural History of Volcanos and Earthquakes. 
__A spring arising from beneath, leads us to conclude that me- 
teoric water penetrates through clefts which communicate low 
down with the former. The experience gained in boring arte- 
san wells, shows that a succession of strata is most favorable for 
such processes, and from causes easily explained. In what are 
- ealled primary rocks, however, no such alteration of strata is 
found, because they are not stratified. The usual occurrence, 
viz., the flowing of meteoric water down inclined surfaces of 
stratification which appear at elevated situations, and the rising of 
this water, by means of natural or artificial channels, after having 
been forced down toa more or less considerable depth, cannot 
then happen in unstratified rocks. It appears, nevertheless, that 
there are granitic rocks traversed by clefts more or less perpen- 
dicular, and communicating low down. Thus at Aberdeen, in 
Scotland, water has been drawn by boring in granite 180 feet be- 
low the surface, which, according to Robison, came from a cleft 
filled with sand and gravel, and rises six feet above the level of 
the earth.* Such a communication of the clefts low down, must, 
‘however, occur but rarely. 
If the primary mountain rises above its environs and the 
clefts at its base lie exposed, then will the springs flow out of the 
clefts. Such an origin of springs, which are not naturally ris- 
ing springs, is often observed at the foot of basaltic and trachytie 
cones, &c. 
On the other hand, on the limits between stratified and un- 
stratified rocks, where the latter have traversed the former, and 
where channels extending to a great depth have been formed in 
_consequence of the contraction of the traversed masses during 
their cooling, circumstances favorable to these rising springs eX- 
ist, and it is easy to conceive, therefore, that thermal springs may 
be found on the limits of these interrupted masses, but not in their 
interior. 
Let us imagine a stratified chain of mountains consisting of 
several formations in a perfectly horizontal position, whose new~ 
est portion (jiingstes Glied) is much fissured, and under which 
an impervious stratum lies, then the meteoric water will penetrate 
the former fissured stratum, but be retained by the latter. AS 
long as this horizontal position remains undisturbed, no rising 
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* Compt. Rend. 183 No. 24, p. 575, and t. ii, No. 20, p. 583. 
