54 WAEM SPRINGS. 



owe their warmth to the same cause, and the dif- 

 ferences between them, in this respect, depend 

 almost entirely on the depths of their sources. 



The fact, that in all parts of the world there are 

 to be found springs, whose high temperature can- 

 not be accounted for by the influence of external 

 heat, justifies, and establishes as universally true, 

 the proposition, from which we started; namely, 

 that the heat of the earth increases with the 

 depth. The hot springs take up for us, as it were, 

 the thread of the proof, which the boring expe- 

 riments, by reason of their limited depth, had left 

 incomplete. 



Spring water usually contains mineral matters 

 in solution. However there are some, even hot 

 springs, which are almost as pure as rain water. 

 Such are the springs at Plombieres in Lorraine, 

 with a temperature of 65° C. (149° F.), that at 

 Gastein of 47°'5 C. (117°'5 F.), at Pfeffers of 

 37°'2 C. (99° F.), at Wildbad (in Wiirtemberg) 

 of37°'5C. (99°'5F.); at Badenweiler (in the 

 Black Forest) of 27°'5 C. (81°-5 F.) and at Warm- 

 brunn in Silesia of 36° C. (96°-8 F.). The Pe- 

 ter s' springs, again, in the Caucasus, having a 

 temperature of 90° C. (194° F.), are almost devoid 

 of solid substances. Other hot springs such as that 

 of Pisa, at44°C. (111°-2F.); of Lucca, at50°C. 

 (122°*9 F.); of Bagneres de Bigorre, at 50° C. 

 (129°*2 F.); of Leuk, at 34°— 50°*5 C. (93°«2 



