1892.] Flame to Detection and Measurement of Fire-damp. 93 



chemical generator, the apparatus being a fixture in a testing room 

 situated near the pit's mouth. 



Since, however, hydrogen gas is now obtainable at small cost, com- 

 pressed in light steel cylinders, it has been found possible to 

 furnish a supply of the gas to a jet inclosed in an ordinary safety- 

 lamp. 



The lamp is so constructed that oil or benzoline may be burnt in 

 the ordinary way from a wick when the lamp is to be used for 

 lighting purposes, the wick being drawn down so as to produce a 

 non-luminous flame, and this yielding caps in gas-testing when pro- 

 portions of gas exceeding 3 per cent, have to be looked for. When 

 proportions of gas less than 3 per cent, are to be looked for and esti- 

 mated, the hydrogen gas is introduced by a metal jet fixed close to 

 the wick ; the gas at once kindles. The wick is then drawn down 

 until the oil flame is extinguished, and the cap is looked for over the 

 hydrogen flame. A cap is easily seen over this hydrogen flame when 

 only 0*25 per cent, of gas is present. When the illuminating flame is 

 required the wick is again pushed up, and kindled by the hydrogen 

 flame. The supply of hydrogen may then be withdrawn. The oil 

 flame and the hydrogen flame are thus made to supplement one 

 another in the same lamp in gas-testing. 



The hydrogen is at present supplied from a small steel cylinder, 

 3 inches in diameter by 8 inches in length, and weighing 4 pounds. 

 The cylinder when fully charged contains 4 cubic feet of hydrogen. 

 This supply lasts for many tests, since when the flame is kept burn- 

 ing continuously at the ordinary height of 10 mm. it consumes only 

 1 cubic foot of gas in about four hours. A regulator may be adapted 

 to the neck of the cylinder, but it has been found that a very delicate 

 valve in the neck of the cylinder serves to adjust the stream of gas 

 with ease without the intervention of any regulator. 



The cylinder is slung in a leather case by a strap across the 

 shoulder. A flexible tube from the nozzle of the bottle connects the 



Fig. 1. 



