74 Natural History of Volcanos and Earthquakes. 



is found, shows pretty evidently the cause of the warmth in the 

 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 Orhe 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 Joax. proves among others, to what a depth the clefts in the 

 limestone rocks descend. 



The whole ridge of the chalk hill of the Teutohurger Wald 

 near Paderhorn, 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 marl 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, He.ler, &c., immediately after their 

 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 Teu- 

 tohurger 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 Paderbor?i, whose 



