Volcanos and Earthquakes. 385 



Calculations of this kind can, from the nature of the subject, 

 give but approximations to the real size of that of which we 

 could otherwise form no estimate at all. The preceding cal- 

 culation shews, at least, that all the clefts and caverns in the 

 chalk rock of the Teutohurger Wald must be filled with water 

 from the level of the springs, down to some impermeable stra- 

 tum. How otherwise can we explain the fact, that consider- 

 able quantities of water of the varying temperature of the at- 

 mosphere constantly sink into the rock, and that as consider- 

 able quantities flow out at the slope of the rock, presenting a 

 uniform temperature, or at all events one which varies only 

 4°.5 Fahr. in a whole year. Since the conjecture is probable 

 that the lias and the variegated marl present the first entirely 

 impermeable strata, we may also conclude, that not only the 

 chalk formation, but also the green sand, which is equally fissur- 

 ed, are filled by the reservoir, and that its bottom is formed by 

 the above-mentioned impermeable strata. Lastly, the high tem- 

 perature of what are called the warm Pader springs {54P.B-^ 

 61°.25 Fahr.) indicates also an origin from a greater depth, 

 if they do not flow in distinct channels, but come from warm 

 streams, which rise from the base of the reservoir. 



The copious springs, which rise on the western declivity of 

 the Teutohurger Wald^ owe their abundance of water, even in 

 dry seasons, to these vast subterraneous reservoirs ; and what is 

 derived from these reservoirs, is abundantly replaced in the 

 rainy seasons, when nearly all the water collected in a district 

 so much fissured, penetrates into the interior. 



These large masses of water, whose temperature exceeds, by 

 several degrees, the average one of the district under which 

 they are collected, and which bring so much the more heat to 

 their surface the deeper they penetrate, have doubtless the ef- 

 fect of warming the hills under which they exist. It is there- 

 fore perhaps a phenomenon of universal occurrence that all chalk 

 hills, which are much fissured, and into which brooks, rivers, 

 and most of the meteoric water sink, maintain a relatively higher 

 temperature. The Pader springs alone, however, shew how in- 

 exhaustible must be the sources which warm such vast masses 

 of water. These springs furnish in a year at least 8688 mil- 

 lions of cubic feet of water, whose average temperature exceeds 



