$6 Additional practical Olservaiiovs on the 



but the workmen very soon vemovcd this inconvenience by the 

 apphcation of a sniall brush. 



We have freciucntiy used the lamps where the ex])]osive mix- 

 ture was so high as to heat the wire-gauze red hot ;-l)Ut on ex- 

 amining a lamp uhich has l)ccn in constant use for three months, 

 and occasionally subjected to this degree of heat, I cannot per- 

 ceive that the gauze cvlinder of iron wire is at all impaired. I 

 have not, however, thought it prudent, in our present state of 

 experience, to persist in using the lamps under such circum- 

 stance?, because I have observed, that in such situations the par- 

 ticles of coal dust, floating in the air, lire at t!ie gas burning 

 within the cvlinder, and fly off in small luminous sparks. This 

 appearance, I must confess, alarmed me in the first instance ; but 

 experience^soon |)roved that it was not dangerous. As it is, how- 

 ever, possible that some other light combustible substance, ca- 

 pable of inflaming at a red heat, may occasionally float in the 

 atmosphere of the mine, I have thought it prudent, for the pre- 

 sent at least, to discontinue the use of the lamps where the gauze 

 is subject to that degree of heat, especially if for a length of tim^ 

 at once. 



Our colliers have found it most convenient to hang the sta- 

 tionary lamps from small vvooden pedestals; but on observing, 

 that where the sides of the lamps have been sufl^ered to come in 

 contact with the pedestals, the wood is charred to a considerable 

 depth by the heat of the lamps; I have thought it right to use 

 small iron pedestals iiistea<l of the wooden ones. 



Beside tlie facilities afforded by this invention to the working 

 of coal mines al)ounding in fire-damp, it has enabled the directs 

 ors and superintendants to ascertain with the utmost precision 

 and expedition, both the presence, the quantity, and the correct 

 situation of the gas. Instead of creeping inch by inch with a 

 candle, as is usual, along the galleries of a mine suspected to con- 

 tain fire-damp, in order to ascertain its presence, we wrdk firmly 

 on with the safe lamps, and with the utmost confidence prove 

 the actual state of the mine. By observing attentively the several 

 appearances upon the flame of the lamp, in an examination of 

 this kind, the c^use of accidents which have happened to the most 

 experienced and cautious miners is completely developed ; and 

 this has hitherto been, in a great measure, matter jof mere con- 

 jecture. 



Wlien the discharge of inflammable air is regular, and the den- 

 sity of the atmosphere continues uniform, the firing point may 

 be judged of, and approached with safety by a common candle. 

 But when the discharge of inflammable air is irregular, or the 

 atmosphere is in an unsettled state, a degree of uncertainty and 

 danger attends the experiment of ascertaining the state of a mine. 



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