80 



In Tuscany there are tlie springs of Monte Catini and 

 Castracaro. 



In Savoy there is Aix les Bains, which is a sulphurous thermal. 



In the Pyrenees there are above 200 hot springs, the most 

 celebrated being the Bagneres de Bigorre, which vary from 

 87° to 123°, the Bagneres de Luchon from 77° to 150°, and 

 Bareges from 87° to 113«. 



In France they are specially found in the district of Auvergne. 

 Vii/hy is the most important of them, of about 170°, and it is an 

 acid alkaline spring rising from Limestone over Granite. 



In Switzerland, in the Canton of Vaud, there are also several 

 thermals principally sulphurous ; in the Valais there are the 

 famous Baths of Leuk, and many others. In Germany and 

 Austria there are the sulphurous thermals of Aix la Chapelle 

 and Borcette, and those of Baden, near Vienna, the alkaline of 

 Carlsbad and Marienbad, the muriated lithia water of Baden 

 Baden, the indifferent thermals of Gastein, of Wildbad, of Tiiffer, 

 in Styria of Landeck, in Silesia of Schlangenbad, in Nassau of 

 Warmbrien, and various others. 



Now from the evidence given by water taken from various 

 Artesian wells and from deep mines, it has been concluded that 

 there is a regular increase of temperature as you descend into the 

 earth. 



The Artesian wells of Crenelle give an increase of 1° for every 

 37 feet of descent, the Durham mines 1° for 44 feet, the Saxon 

 lead mines 1° for every 65 feet, the mine of Dolbrouth 1° for 

 75 feet, the Wheal Clifford mine 1° for 22 feet — an average 

 taken upon a large number of mines and wells gives 1° for every 

 45 feet of descent. 



As a result of such a rate of increase, taking the mean tem- 

 perature of the earth at 80 feet deep (that is beyond the influence 

 of the sun) at 50°, it follows that at 7,290 feet deep the heat will 

 reach 212°, the boiling point of water, at 25,500 it Avill melt 

 lead, at 21 miles it will melt gold, at 47 miles it will melt 



