286 M. L. Cordier, Examination of recent Experiments 



In the course of my investigations in the mines just mention- 

 ed, as well as in several others to which I have extended my re- 

 searches within these six years, I determined another not less 

 interesting fact, namely that, at the same time, the temperature 

 of the air is scarcely ever the same at the lower and upper parts 

 of a gallery, or any other work of the same kind. In a height 

 of less than six feet, I sometimes found differences of 5° or even 

 T. At the Ravin mine, for example, in the whole extent, and 

 at the extremities of the unfrequented galleries, the thermome- 

 ter, placed at a distance of 8 inches from the floor, marked from 

 16 to 22 tenths Fahrenheit less than near the roof. At the 

 extremity of the waggon-way of the lower stage, the differ- 

 ence was 3°.4. This remarkable difference prevailed over a 

 great extent, and as a considerable slope favoured the passage of 

 the cooled air toward the ventilating chimney, there resulted 

 at the floor of the gallery, a current which could be ren- 

 dered sensible by means of a little smoke *, and which sup- 

 plied the defect of communication between the extremities of 

 the two stages. The warm air which occupied the upper part 

 of the gallery had a motion in the contrary direction, and flowed 

 to undergo the effect of cooling which the freshly exposed sur- 

 faces at the extremity of the perforation operated upon it. The 

 same effects took place at the upper stage, which made the 

 workmen entertain the apparently absurd opinion, that the air 

 came from the bottom of the works. 



The last mentioned experiments are also those which have 

 contributed the most to make me discover that the influence of 

 the causes which occasion the temperature of the air in mines to 

 vary incessantly, assuredly extends to the bottom of the most 

 distant works. The consequences which are to be deduced from 

 them with reference to the merit of the observations under dis- 

 cussion, are too evident to require any particular exposition. Thus, 



• To appreciate the direction and velocity of the currents of air in mines, 

 there may be employed with great success, the smoke produced by the defla- 

 gration of a mixture formed of well pulverized metallic antimony and gun- 

 powder, in the proportions of two to five. This mixture, which was pointed 

 out to me by M. D'Arcet, was put to the proof by the commission of which 

 we formed part in 1826, for the curing of the sewers of the City of Paris. It 

 will be almost always sufficient in mines to bum a very small quantity of it. 



