284 M. L. Cordier, Examination of recent Experiments 



dently results from them a multitude of motions, of particular 

 currents, and counter currents, almost always unperceived by the 

 miner, which extend into all the parts of the excavations, and with- 

 out which, I now believe, that the ventilation of mines would be 

 very imperfect. I calculate, besides, that, in more than one im- 

 portant mine, when the external temperature is from 68° to 77° 

 Fahrenheit, the air which is introduced in the course of an hour 

 is not equivalent to the hundredth part of that which fills the 

 excavations. 



To support the observations which I have just expressed, I 

 shall relate the result of some experiments. 



On the 9th November 1822, at seven in the morning, when 

 I descended into the working called the Ravin, in the mine 

 of Carmeaux, the external air six feet above the surface of 

 the ground was 56°.l Fahrenheit. Five hours after, when I re- 

 turned, it was 58°.8 Fahrenheit. 



A single shaft which, not including the puisard, was 482 

 feet deep, cleared the whole works. At the middle of the 

 entrance of this shaft, the air entering at the same hours as above 

 marked 2°.2 Fahrenheit more than without. Thus it was al- 

 ready mixed with the warm air, which arrived in an insensible 

 manner from the bottom of the works. 



The works were intended to prepare the extraction of two thick 

 beds of coal, nearly horizontal and parallel, and at an average 

 98 feet distant from one another. They consequently consisted 

 of two stages, formed each of wide galleries, crossed at right 

 angles, and traversed by a principal waggon way. These ex- 

 cavations, the digging of which had been pursued with constant 

 activity for seven years and a half, were then very nearly 558,450 

 cubic feet in extent. The ventilation was effected in the usual 

 manner. From the surface of the section of the ventilating chim- 

 ney, and the velocity of the air which issued from it, I found 

 that the quantity of air introduced into the mine in an hour 

 was only 3705 cubic feel, that is to say, it was not equivalent 

 to the twelve thousandth part of the mass contained in the ex- 

 cavations. 



Nineteen lamps and twenty-four workmen distributed in the 

 two stages, were constantly employed during six days of the 

 week, and produced hourly a heat capable of raising 2°.99 Fah- 



