44 M. L. Cordier, Exariimations of recent Experivients 



of the radiated iron pyrites in mines, are far from being of 

 frequent occurrence, and that when they do occur, it is but rarely 

 that they act on great masses. There is nothing, besides, more 

 easy to discover and determine than effects of this kind ; the rock 

 crumbles, and is resolved into earth or gravel ; saline efflores- 

 cences manifest themselves in great abundance ; the waters be- 

 come strongly vitriolic, and their circulation gives rise to vari- 

 ous inconveniences, against which the miner has to provide ; 

 lastly, in however small a degree a mass of rubbish or broken 

 down rocks happens to assume a temperature superior to that of 

 the surrounding works, there is none of the workmen that does 

 not perceive it. 



Thus, for example, when I descended into the mines of 

 Decise on the 1st September 1825, my questions respecting the 

 matter in question, were prevented by pointing out to me a por- 

 tion of the old works, at a great distance from that in which I 

 made the experiments, of which I have given an account, where 

 the miners wrought stark naked. The cut was in the midst of 

 an old mass of coal, having in its centre a heap of rubbish that 

 had long been heated. To the hand the surface of the cut 

 which had just been laid bare felt warmish. With the thermo- 

 meter, the interior of the coal marked 80°6, that is to say 14°4 

 more than the proper heat which the rock should have presented 

 at this level. The air which circulated with difficulty in this 

 small work, indicated 82°4. 



I shall conclude what it was necessary to state on this sub- 

 ject, by remarking that part of the observations which we have 

 discussed, were made in excavations where there were no pyrites, 

 or in mines where it existed in so small quantity or was so in- 

 capable of decomposition, that it may be overlooked. This re- 

 mark necessarily applies to the conduits of such diversified na- 

 ture, in which the waters that filtrate in mines, and even in 

 general those of superficial springs, acquire their temperature. 

 With regard to mines in which there exists pyrites in any con- 

 siderable quantity, the observers assured themselves that no in- 

 fluence could result from it upon the temperature of the exca- 

 vations in which they experimented. The character of the ob- 

 servers can leave no doubt on this subject, and their testimony 

 is in harmony with what we have just stated. 



