1893.] A New Portable Miners Safety-lamp. 503 



The Measurement of the Percentage of Gas in Air by the Spiring of the 

 full Luminous Flame. 



It has recently been stated that the " spiring " of the fall bright 

 flame of the lamp is a very delicate and trustworthy test for gas. 

 This effect occurs when the flame, which has been raised to the 

 verge of smoking in air free from gas, is brought into air containing 

 gas. The flame then stretches upwards a thin tongue, assumes a 

 redder tinge, loses in brightness, and begins to smoke. It is stated 

 that 0'5 per cent, of gas may thus be detected with ease and 

 certainty. Experiments in the test-chamber failed to detect 0*5 

 per cent, of gas with an ordinary colza-petroleum flame. With a 

 benzoline flame, however, 0*25 per cent, was detectible ; and the 

 spiring of the flame with 0'5 per cent, was most pronounced ; while 

 with 1 per cent, of gas a very distinct red spiring flame was produced 

 which smoked freely. But it was at once evident that any safety-lamp 

 flame when delicately adjusted for this test was very easily made to 

 " spire" by causes other than the presence of firedamp; this was 

 especially the case with the benzoline flame, which seemed to spire 

 spontaneously at any moment. 



When it is remembered that the " spiring " may be caused by any 

 slight increase in the oil supply to the wick, or by the reduction of 

 the supply of air or oxygen to the flame, arising from any cause other 

 than the presence of " gas," ifc will be seen that the indications cannot 

 be very trustworthy. The method is further impossible of application 

 in many situations, since the flame must be adjusted for the test im- 

 mediately before it is applied, and this must be done in air free from 

 gas. Air known for a certainty to be free from " gas " is not obtain- 

 able in many situations where the test would have to be carried out. 

 This test further clogs the meshes of the gauze with soot, and this 

 impedes the proper action of the lamp. 



The conclusion, drawn from a series of comparative experiments 

 made in the test- chamber, was that the flame-cap test when carried 

 out in the way already described, and with the apparatus mentioned 

 above, exceeded both in delicacy and in trustworthiness the test 

 depending upon the "spiring" of the full bright flame of the safety- 

 lamp. 



I have much pleasure in acknowledging the valuable and intelli- 

 gent assistance rendered by W. T. Kigby in the above investigations. 



