M. L. Cordier on Subterranean Temperature, S3 



by the contact of the soil over which they have flowed, by the 

 effect of evaporation, or by the influence of the surrounding air. 

 Thus, for example, they may be far above the proper tempe- 

 rature of the level of observation, if they have come frequently 

 into contact with an air much heated by the effect of the season, 

 and at the same time by that of the lights, and the presence of 

 the workmen ; and if the walls of the excavations have had 

 time to contract a heat superior to that which they originally 

 possessed. The observations of the kind in question are there- 

 fore subjected to too many causes of uncertainty to afford re- 

 sults having any degree of accuracy, with reference to the law 

 which the increase of temperature follows in the bosom of the 

 earth. 



Let us now examine the three cases which we have distin- 

 guished with relation to the stagnant waters. 



1st, The small pools that are met with in mines, it is evident, 

 can only give very defective indications, for these indications 

 may vary according to the following causes, viz. the original 

 temperature of the water ; that of the rock, if it has been mo- 

 dified ; that of the air ; and the influence of evaporation. It 

 may bcvsides be conceived, that, however shallow the pool may 

 be, the temperature of the surface may be higher than that of 

 the bottom. I shall adduce two examples to illustrate these 

 considerations. 



At Carmeaux, in the Ravin mint*, where, on the 9th No- 

 vember 1822, I found the proper temperature of the rock at 

 62°.8 Fahr. ; and where the air marked near the bottom of 

 the galleries, from 70°.7 to 1V.6 Fahr. ; and near the roof, 

 from 73°.4 to 74M ; I noted from 65°.5 to 6T.\ in very small 

 pools. 



At Littry, in a gallery at the bottom of which I found the 

 proper temperature of the rock 61°.043, the air marking 70^97 

 near the roof of the gallery, I found that the temperature of the 

 water of a small waggon-way, 15 inches in depth, rose to 63°.63. 



In these two cases, the temperature of the water would have 

 given an erroneous indication of the proper heat of the rock. 



We are therefore authorised to reject the employment of al- 

 most the whole of the observations of this kind. The numbers 



OCTOBER DECEMBER 1828. C 



