which are evolved in Goal- Mines. 311 



the fissure, or from the tube, which was five lines in diameter, 

 could, with facility, be extinguished. It was extinguished by 

 blowing upon it at a distance of from three to six feet, or by 

 making a movement in the air with the hand. This appear;^ 

 less remarkable when we take into consideration, that the 

 gas flows out with no higher pressure than that of the atmo- 

 spheric air. The slightest current of air, therefore, is suffi- 

 cient to blow out the burning gas. It is different, as is well 

 known, when inflammable gases are evolved from apparatus 

 intended for the formation of gases, and when they issue out 

 under a greater or less degree of pressure. In order to ex- 

 tinguish such a current of gas, a current must be employed 

 which is greater than that of the gas itself. It is further 

 known, that this current must be so much the greater in pro- 

 portion as the inflammable gas evolves heat during its igni- 

 tion, and as it is more easily inflamed. Hence, of all the in- 

 flammable gases, hydrogen is the most difficult to extinguish. 

 The heat evolved by the flame of the burning pit-gas is in- 

 considerable ; for one can extinguish it by slowly closing the 

 tube with the finger, without burning himself. • 



The current of gas can neither be set on fire by lighted 

 tinder nor by a lighted cigar, even when we attempt to 

 kindle it by strongly blowing with the mouth. If we do not 

 blow, both are speedily extinguished by the current of gas. 



The temperature of the current of gas was ascertained by 

 me to be 55°.7 F., by placing, for some time, the bulb of a 

 delicate thermometer in the gas. The same thermometer 

 indicated a temperature of 54°. 7 F. in a bore in the rock 

 near the fissure, which was eight inches deep ; as deduced from 

 three observations made in the morning, at noon, and in the 

 evening. It being assumed that the gas brings with it the true 

 temperature of the place where it is originally evolved, that 

 the mean temperature of the ground of the outer crust of the 

 earth at SaarbriJcken is 49°. 5 F., and that the increase of 

 temperature towards the interior of the earth amounts to 

 1° F.,* for fifty-one Parisian feet, it would result that the 



* The place where the gas comes out, is of course, at a depth where no 

 changes of temperature occur. However, the communication by the air 



