282 M. L. Cordier, Exainhiation of recent Experiments 



a more or less sensible manner, the temperature of the air con- 

 tained in the different parts of each stage^ but it also tends ulti- 

 mately to lower the proper temperature of the whole excavations, 

 and this in a necessarily unequal manner in the different parts 

 situated at the same level. 



The second disturbing cause, the filtering water, acts in a uni- 

 form manner, whether we consider its action in a very short, or 

 in a very long period. It also tends to diminish the temperature 

 of the air contained in the excavations in which it occurs. 

 It depends upon the influence of the proper heat of the affluent 

 waters. Now, it will be seen hereafter, that these waters arrive 

 at the point where they make their exit, with a temperature ac- 

 quired in more elevated zones of rocks ; consequently, the sur- 

 faces which they cover in each excavation, communicate to the 

 air in contact a temperature lower than that of the surround- 

 ing rock. 



The third disturbing cause, viz. the heat disengaged by the 

 workmen and the lights they use, exercises an influence the re- 

 verse of the preceding, an influence often powerful, and which 

 has not yet been calculated, although it has served as a basis to 

 several persons for denying the consequences deduced from ex- 

 periments made upon subterranean temperatures. It is essential 

 to value its effects approximatively by numbers. 



According to the interesting researches of M. Despretz on a- 

 nimal heat, a middle sized man disengages, in twenty-four hours, 

 by respiration, a quantity of heat equal to that which would 

 raise 1 ounce of water to 205,709° Fahrenheit, and this heat is only 

 three-fourths of the total heat produced in the same period, by 

 the same individual. Whence it follows, that the total heat 

 which is disengaged in an hour, is equivalent to what would 

 raise 4640 pounds of water (in round numbers), to 1° Fahren- 

 heit. Making use of the proportion (1,0000 : 2,669) which, ac- 

 cording to MM. de La Roche and Berard, expresses the differ- 

 ence of the specific heats of water and air, and setting out from 

 the specific gravity which air possesses at 54° Fahr. of temperature^, 

 it is definitively found, that a miner disengages hourly a quan- 

 tity of heat capable of raising 1° Fahr. 34,456 cubic feet of air, 

 taken at 54° Fahr. of original temperature. 



