74 ‘ Natural History of Volcanos and Earthquakes. 
is found, shows pretty evidently the cause of the warmth in the 
w 
latter. 
It is scarcely to be doubted, but that, on closer investigation, 
the phenomenon of local heat in caves in the limestone rocks, 
which are fissured to such great depths, would be found to be of 
more frequent occurrence. The spring of the Orbe in the Jura 
mountain, formerly mentioned, which is nothing more than the 
discharge of the lakes situated 680 feet higher in the valley of 
the Joux, proves among others, to what a depth the clefts in the 
limestone rocks descend 
The whole ridge of the chalk hill of the Teutoburger Wald 
near Paderborn, is fissured to depths exceeding 800 feet, so that, 
on this whole ridge, either no springs at all, or but a few very 
scanty ones, are met with, which probably owe their existence 
to partial beds of mar] in the chalk rocks. In three villages 
which lie on this ridge, there is but one well 80 feet deep. On 
account of this almost total want of water, these are called the 
“ Dry Villages.” The cleavage continues in the valleys, which 
traverse these hills, consequently the brooks and rivers which 
flow through them gradually sink and flow out of the open- 
ings of these valleys only in the wet season of the year. At 
the foot of these chalk hills on the other hand, where the fissured 
limestone is covered by a stratum of marl, a very great number 
of copious springs issue, several of which form considerable riv- 
ers, as the Lippe, Pader, Heder, &c., immediately after theif 
exit. The cleavage of the chalk rocks is doubtless continued 
in the Quader Sandstein, which lie below and probably is lim- 
ited by the lias (gryphitenkalk) and veriegated marl, which fol- 
low immediately below the green sand, and which are remark- 
able for their large strata of clay marl (thonmergel,) that are 
impermeable, unless broken or dislocated by elevations. This 
whole chain of hills, then, from the clay-marl strata to the level 
of the springs which issue on the western declivity of the Tet 
toburzer Wald, is, therefore, saturated with water like a sponge 
Not merely geognostical reasons, but also physical relations, fur 
nish incontestible proofs of the existence of these considerable 
subterraneous reservoirs of water. For instance, while the water 
of the above-mentioned sinking brooks and rivers penetrates into 
the interior of the hills with the variable temperature of the sea 
sons, the waters of the numerous springs of Paderborn, whose 
