380 Prof. Bischof on the Employment of the Safety-Lamp 



which might be closed up by cork-stoppers. The bottom had 

 three holes, one of which was for drawing up the safety-lamp, 

 the second for admitting the inflammable gas, the third for 

 the penetration of the atmospheric air into the cylinder. 



This apparatus was fastened near the blowers, and the in- 

 flammable gas introduced through a tube stuck into the fissure 

 from which the gas was issuing. The safet3'-lamp suspended 

 to a wire going through the cork-stopper in the middle hole, 

 was drawn up into the cylinder. By opening or closing the 

 other holes, the circulation of the explosive mixture formed 

 in the interior of the cylinder, was regulated in such a manner 

 as always to surround the safety-lamp with new quantities of 

 it. 



There were different layers of gas in the cylinder ; at the 

 top for the most part the light inflammable gas, at the bottom 

 chiefly the atmospheric air, but in the middle there was an 

 explosive mixture of the strongest exploding power. It was 

 therefore evident that the safety-lamp near the bottom scarcely 

 ascertained the actual presence of the fire-damp, whilst at the 

 top it was soon extinguished. But in the middle of the cylin- 

 der the phenomena depending on the presence of the explosive 

 mixture took place in the most powerful degree. The flame 

 of the lamp increased not only to the top, but it was there 

 bent down, and the whole cage filled with fire. 



In this part of the cylinder the safety-lamp remained from 

 fifteen to twenty minutes, provided that no inflammation 

 through the wire-gauze took place. The latter was for the most 

 part red-hot. The lamp was for some time put in pendulum 

 motion, which was as violent as possible, in order to imitate 

 the passing of the workmen in the mines where inflammable gas 

 prevails. On another occasion the lamp was held obliquely, 

 in order that the increased flame might reach the wire-gauze. 



I wished to examine the safety-lamps, not only relatively to 

 the greatness of the apertures of their wire-gauzes, but also 

 to that of their diameters. I had six kinds of wire-gauze of 

 brass made, and five cylinders were made of different diame- 

 ters of these six sorts. Therefore thirty cylinders were ob- 

 tained, the number of the apertures and the greatness of the 

 diameters of which are the following : 



