58 L. M. Cordier, Examination of' Recent Experiments 



mine of Beschert Gluck, for example, has been open for two 

 centuries ; at the period when the experiments were made, there 

 were constantly in it nearly SOO workmen and 200 lights du- 

 ring five days in the week, and this state of things had existed 

 for about thirty years. Thus, therefore, although the thermo- 

 meters were invariable in the different points, at least according 

 to M. de Trebra''s assertion, there is very little probability that 

 the experiments precisely indicated the original temperature of 

 the rock at each level of observation. If we consider the great 

 extent of the works, the enormous magnitude of the excavations, 

 the abundance of water, and all the other accessory circum- 

 stances, we shall be induced to regard the markings collected as 

 being beneath the original temperature which it is our object to 

 discover. The results are consigned in the table which we shall 

 presently give. 



^d, In a mine of Cornwall, that called United Mines, the 

 temperature of the rock of two galleries, which were inundated 

 for two days, was taken ; and, for this purpose, the thermome- 

 ter was sunk several inches in the earthy matters forming the 

 £oor of these galleries. It is evident that this experiment, 

 mode in a cursory manner, involves several sorts of uncertainty. 

 In all probability, the temperature observed represents the ori- 

 ginal temperature of the level at which it was made only ap- 

 proximately. Previous to the inundation, the rock had already 

 a temperature compounded in the ratio of all the causes which 

 had acted upon it from the opening of the galleries. After the 

 inundation, the presence of the water necessarily produced some 

 modification, for it is almost impossible that it had arrived with 

 a temperature equal to that of the works which it filled. In 

 support of these considerations, I shall mention the results of the 

 following experiments. 



At the Ravin mine, near Carmeaux, in the lower stage of 

 which I have already spoken, at 56 feet from the slope (taille), 

 the thermometer sunk about 8 inches in the humid and beaten 

 rubbish which formed the floor of the gallery, marked 4°. 7 more 

 than the temperature proper to that level. Operating in the 

 same manner in more distant parts, I found 5°, and up to 5°6 

 of difference equally in excess. I should probably have had 

 smaller differences, or even differences of a contrary nature, if, 

 in place of observing in autumn, I had operated at the end of 

 winter, and after continued frosts. 



