Hot and TJtermal Spring's. 135 



innvimerable, then, may not be the effects of thermal waters 

 upon the interior strata of the earth ? 



In the copper mine at Oatfield, at a depth of 1392 feet, and 

 72 feet east of the shaft, the temperature was found, in May 

 1822, to be 79°.92 ; whilst in an end, situated only 24 feet 

 deeper, 180 feet to the west of the shaft, it was 85°.10. Here 

 the water, which issued in considerable streams from two nar- 

 row clefts in the floor of the gallery, but a few feet distant from 

 one another, shewed the unequal temperatures of 81°.95 and 

 86°.45*. In the neighbourhood of some tepid springs in the 

 Churprinz^Frkdrich- August adit, in the Erzgebirge, the tem- 

 perature of the air was exactly 68°.0 ; and when the waters 

 had acquired an uninterrupted afflux, they soon warmed the 

 rock to such a degree that their temperature remained constant-f*. 

 How great, then, must be the influence of considerable masses 

 of water of an elevated temperature, such, for instance, as those 

 of Aiac-la-Cliapelle, Burtscheid, Wiesbaden, Carlsbad, &c., on 

 the rock beneath the sux'face. 



Waters which descend into the earth through clefts operate 

 more or less with a cooling effect, and, on the other hand, waters 

 rising from great depths operate more or less with a warming 

 effect, upon the rock. 



Innumerable modifications may be caused in the thermome- 

 trical circumstances of the interior of tlie earth by various com- 

 binations of cases ; we will here mention a few for the sake of 

 example : — 



1*/, Let EE, PI. II, Fig. 2, be the bottom of a valley, cut ofl" 

 from communication with the surrounding hills by the imper- 

 vious strata d,d,d, but the soil of which admits of the infiltra- 

 tion of the meteoric waters until they reach those impervious 

 strata. In this case the meteoric waters will only sink into the 

 earth without being able to return to the surface. The soil 

 through which these waters have passed can therefore suffer 

 no alterations of temperature but from without, as all waters 

 which might bring heat from below are intercepted by the im- 

 pervious strata d, d, d. 



2t/, The contrary case will happen when the impervious strata 



* Gilbert's Anna!., vol. Ixxvi. p. 431. t Reich., p. 153. 



