AND ON PREVENTING ITS EXPLOSION. 41 



This method, in its simplest form, affords another security, 

 that of avoiding the igniting of any stream or blast of inflam- 

 mable air, as it issues from the coal. This it often does sud- 

 denly, and with great violence. A current of this air being 

 kindled in the common mode of lighting the mines, by the ap- 

 proach of a candle or lamp, is a frequent cause of explosions, 

 the stream of flame extending to the mixture of inflammable 

 air and common air in the roof of the mine, and causing it to 

 explode. The inclosing of the lamp in the case, of course, pre- 

 vents any accident of this nature. 



By these arrangements, adapted more or less to circumstan- 

 ces and situations, a system of lighting mines may be establish- 

 ed, I trust, perfectly safe, with any common care. And the 

 extreme simplicity of the plan, facility of execution, and eco- 

 nomy, are recommendations in its favour. 



It is scarcely necessary to enter on the details of the modes 

 of construction of the apparatus, as these are both obvious, and 

 admit of considerable diversity. I have given what appears to 

 be the best figure of the glass case for a fixed lamp, sufficient- 

 ly wide to prevent it from being broken by the heat, and not 

 too much so, so as to lessen the current and rarefaction of the 

 air. The aperture, too, is adjusted to the same purpose. If a 

 lamp with oil be employed, it can either be suspended from 

 the top, or fixed on a socket from beneath ; if a candle be 

 used, it must have a socket, which it may be requisite should 

 be a sliding one, to adjust it to the due height, as it burns 

 down. The glass cases may be protected from external inju- 

 ries by a wire netting. Fixed lamps will in general be less ex- 

 posed to risk than moveable lights, and by employing them in 

 sufficient number, few of the latter may be required. In all 

 the passages of the mine the former may be employed ; and in 

 all cases where fixed lamps with a metallic tube reaching nigh 

 to the floor can be introduced, the method is more simple, and 



Vol. VIII. P. I. F is 



