Hot and Thermal Springs. 141 



Arago, with justice, considers this phenomenen of great im- 

 portance, and remarks, that its further investigation would not 

 only serve to prove the existence of a superior temperature in 

 the interior of rocks and metalliferous veins, but would afford 

 an additional objection to the hypothesis, supported by several 

 philosophers, that the higher temperature in mines is the re- 

 sult of the action of the air upon substances, particularly the 

 pyrites, on the walls of the galleries. To prove that the ob- 

 servation alluded to indicates a more important source of heat 

 in the interior, he adds two mathematical formulae from Fou- 

 rier's Theorie de la Chaleur, from which it follows that, cceteris 

 paribus, the temperature of the mass of a lode which is in con- 

 tact with the atmosphere is greater, the more easily heat is con- 

 veyed into the interior of the mass. Cordier,* in his observa- 

 tions on mines, also mentions the great influence of a metalli- 

 ferous zone on the subterranean temperature, owing to its su- 

 perior conductibility of heat. 



From the observations on the internal temperature of the 

 earth, carried on in various mining establishments in the Prus- 

 sian dominions, it has also been found, that the increase of tem- 

 perature is, in general, much more rapid in coal than in metal- 

 liferous mines. -f- Von Dechen, the publisher of these observa- 

 tions, leaves it undecided whether this greater increase of heat 

 is produced by the decomposition of the pyrites and coal, in 

 which case it would not exist before the opening of the mines, | 

 or whether it is a consequence of the locality of the mine. If 

 we take into consideration the difference of the facility with 

 which heat is transmitted by coal and metals, we shall be in- 

 clined, agreeably to the observations communicated above, to 

 look upon this as the real cause of the phenomenon. From 

 observations in five coal-mines, the result was, that an increase 



• Mem. de 1' Acad. Roy. de Sciences de Paris, vol. vii. p. 473. 



+ Poggend. Annal. vol. xxii. p. 497 and following. 



J D' Aubuisson (Journ. des mines, vol. xxi. Annal. de chim. et de phys_ 

 vol. xiii. p. 184. See on the other liand, Fox, in Gilb. Annal. vol. Ixxvi. 

 p. 427, 442, and 448.) found, in a mine near JIuelgoat in Bretagne, the tempe- 

 rature in the upper works to be &°8 ; but at the depth of 230 metres 15°8, 

 and the water vitriolic. See Chap. III. 



