1815.5 Carbureted Hydrogen Gas in Coal-Mines. 3SS 



the size, one general rule may be adopted, vvliich is, not knowingly 

 to get past the limits of certain experience, unless the object to be 

 obtained is much greater than the risk run. The size of the top 

 appears to me to depend in a great degree on the heat of the mine. 

 1 have examined the top in parts of a mine where the air was 

 stagnant but pure, and I always found it greatest in the hottest part. 

 In making these experiments I have often seen it three, sometimes 

 four, and once five, inches above the flame, without any ditference 

 in the colour except in intensity, which increased with the size of 

 the top. I once advanced towards the forehead of a woiking in 

 which the air was still, with a candle having a deep yellowish- 

 brown top, four inches long, till I observed longitudinal streaks of 

 bluish-green were mixed with the yellowish-brown. I then began 

 to retreat, being convinced that my situation was dangerous. I 

 have often thought the moisture in the air of the mine affected the 

 top ; but I never met with proper situations to make so many expe- 

 riments as would enable me to come to very accurate conclusions. 



When a miner is about to use his candle he snutFs it, and then 

 waits till the top of the wick is inflamed. As on such an occasion 

 as this he generally carries his candle as near the ground as his arms 

 will ])ermit, he never raises his candle, but depresses bis body till 

 his head is nearly on a level with the candle, and probably he may 

 kneel on one knee; he then, holding the candle in the manner 

 before described, and having his eye steadily fixed on the top, rises 

 slowly, till the candle is nearly as high as his face when he is stand- 

 ing upright. If he finds the top has a favourable appearance, he 

 gently sinks his candle again, and advances a few yards; but if the 

 top indicates the presence of the inflammable gas, he experiments 

 more cautiously, and advances a less distance between every trial ; 

 if the tjuantity of gas appear to be increasing, he advances very 

 slowly, with his eye constantly fixed on the top, and his body rather 

 bent forward ; and if the quantity be still increasing, and the appear- 

 ance of the top rather alarming, he advances still more slowlv, and 

 pauses at every yard in length, to be more exact in his examination. 

 And if the quantity of gas reach its maximum before he considers 

 the top to be dangerous, he advances slowly to the end of his 

 journey ; i(Ut if it continue increasing, he will be forced to return. 



Much steadiness is required in these trials; for sometimes the top 

 suddenly assumes so alarming an aj-.pcarancc, that a person may be 

 intimidated so much as to make a precipitate retreat ; and in doing 

 ho sct> the gas on lire, by bringing a quantity of it, or a sop, as the 

 miner calls it, upon his candle, Ijy his rapid movement. Before he 

 tries, he should first consider what he ought to do in every probable 

 exigency ; so when the top stuKlenly ;i])pears dangerous, be will 

 sink the candle slowly to the ground, and bend his body as uuuhas 

 he can at the same lime, then turn about and retreat as slowly j 

 avoiding, if pussible, the direction that he advanced in during the 

 dangerous part. 



