iVire-gauze Safety -Inmps for Miners. 53 



be unfounded ; the carbonaceous matter produced from the de- 

 composition of the oi!, tends not only to prevent the oxidation of 

 the metal, but likewise revives any oxide already formed ; and 

 this coaly matter, when the fire-damp is burninii; in the lam]>, 

 choaks the upper apertures of the cylinder, and gradually di- 

 minishes the heat, by diminishing the quantity of gas coqsumed. 



In my early inquiries on this subject, I thought that some vi- 

 treous incombustible composition might be used as a. coating to 

 prevent the rusting of the wire, and I made some experiments 

 on this subject. I find that a fusible conjpound of boracic ficid 

 and the earth called baryta, answers the purpose of a coating 

 very well ; and if in anv case experience should prove that such 

 an application is necessary, it may be easily made. 



It is obvious, that as long as the principle of security (which i$ 

 to admit no aperture in alamj) of more than tt'tj ^f^^^ bicli square) 

 is preserved, the construction may be almost infinitely varied, 

 and the fire-damp may be burned throughout the whole of a cy- 

 linder, or inflamed at certain surfaces only, and the light trans- 

 mitted from other surfaces through horn, or mica, or glass. I 

 long ago had a lamp madeof glass, in which the fire-damp burnt 

 round the wick only, from a circular surface of wire-gauze, and 

 which, in an explosive u)ixture, produced very Httle more heat 

 than in the common atmosphere j but the facility with which 

 glass is broken, and horn and mica injured, prevents me from re- 

 commending any lamps in which these substances are used for 

 the common purposes of the miner. 



I have tried a chiainey of brass capped with a double wire- 

 gauze cylinder, having two-thirds of its circumference opposite 

 the flame open, and covered with wire-gauze. This, in an ex- 

 plosive mixture, produced very little heat, though it gave a tole- 

 rable light, and by increasing the surfaces impenueable, or by di- 

 minishing those permeable to air, the heat may be reduced in 

 any degree*. 



Whatever construction is adopted, too much attention cannot 

 Ije |)aid to the form of the screw by which the cylinder or chim- 

 ney is fastened to the lamj) ; it ought to be strong and deep, 

 and to consist of at least three turns. 



When the firc-dan)p is inflamed in the n-irc-gauze cylinders, 

 coal dust thrown into the lamp burns with strong flashes and 



• TlieJlcv. Joiiii II()di;son, whose iou\ and activity in promotin<; the oh- 

 jctts of these rcseari'lies I Cimtiot [)iiiisc too hi};hly, has liad a Ininp made 

 tipmi this plan, liaviiii!; a tiiick plate of chi^s in a riietnllic chimney opposite 

 a wirc-ganze t'cKler, in whirli the supply of air is roiii;!atcd by means of a 

 fclidcr. 1 found a niodd whiih ho sent me to answer very well; the only 

 objectioH is, the chance of tiic {^lass being brokwi by a fail, or l)y a drop of 

 vvatcr when hot. 



P 3 8cln- 



