42 M. L Cordier, Examination of recent Experiments 



the 4th of August 1792 * A stream of water, capable at its 

 source of turning a mill, and which is situated near Macug- 

 naga, at the bottom of the great snowy amphitheatre of Mount 

 Rosa, marked only 38° 75' F. by the thermometer. Large 

 springs flowing at the foot of a great limestone chain, about 550 

 metres above the sea, at the bottom of the valley of the Arve, 

 near Sallenche in Savoy, marked 45° 9' F. 



To these facts I shall add the following, which is more re- 

 markable. The beautiful fountains of Medouze, situated in the 

 High Pyrenees, near Bagneres de Bigorre, at the entrance of the 

 Valley of Campan, and at the very level of the bottom of that 

 celebrated valley, produce a rapid stream of water, which, at its 

 source, turns three mills in a space of 200 yards. On the 22d 

 September 1822, at ten in the morning, I found their tempe- 

 rature 50° 7' ; that is to say, about 7° below the mean tem- 

 perature of the bottom of the valley. The strong current of air 

 which issued with the water was of the same temperature. 



Anomalies of this kind are easily explained from local circum- 

 stances. No plausible objection can result from them, against 

 the general inference to be drawn from the heat of all the fresh 

 water springs, and all the currents of water coming from the in- 

 terior of the earth. 



Fxf'th and Last Consideration. — Formerly, when mineralogy 

 was limited to the study of some rare and sparkling substances, 

 pyrites were everywhere seen, even in lavas, although these pro- 

 ductions were completely destitute of them, and it was imagined 

 that several great phenomena, depending upon the constitution 

 of the earth, could be accounted for by supposing subterranean 

 fermentations produced by the decomposition of these pyrites. 

 These two kinds of prejudices are now properly discredited, at 

 least among those who are acquainted with the full progress of 

 geology. In fact, pyrites are infinitely less abundant than has 

 been supposed, especially in masses of any extent. They are 

 for ever unalterable, so long as they remain enveloped in the 

 rocks which contain them. Placed in the most favourable cir- 

 cumstances, two of the three species of pyrites that have been 

 discovered are permanent, or are only decomposed with extreme 

 difficulty. One species only, radiated pyrites, is capable of being 



• Voyages dans les Alpes, sect. 1403 and 226. 



