192 On Sir H. Davys Safe-lamp for Mines. 



or of coal-gas, it prevents the flame from passing it, and tliO 

 phaenomenon is precisely similar to that exhibited by the wire- 

 gauze cylinders; the air passing through is foinid very hot, for it 

 will convert paper into cliarcoal ; and it is an explosive mixture, 

 for it will inflame if a lighted taper is presented to it, but it is 

 cooled below the explosive point hy passiiig through wires even 

 red hot, and by being mixed with a considerable quantity of air 

 comparatively cold. The real temperature of visible flame is 

 perhaps as high as any we are acquainted with — Mr. Tennant 

 was in the habit of showing an experiment, which demonstrates 

 the intensity of its heat. He used to fuse a small filament of 

 platinum in the flame of a common candle ; and it is proved by 

 many facts, that a stream of air may be made to render a me- 

 taUic body white hot, yet not be itself luminous." — I forbear to 

 quote more of this interesting paper, though I recommend the 

 whole to the careful perusal both of Mr. Holmes and the other 

 opposers of the " wonderful lamp." — The experiment I have de- 

 tailed is correctly explained by the above reasoning. Even at 

 a red heat the wire cooled the gas below the point of inflamma- 

 tion, — but not when the heat nearly reached to whiteness, and 

 accordingly explosion then ensued. Mr. Holmes has not, after 

 all, made any great discovery in finding that the inflammatioii 

 of the gas will penetrate the wire-gauze when reacted on by a 

 strong current of air — for Sir Humphry Davy has stated it 

 himself in his " Additional Practical Observations," printed 

 first for distribution amongst the miners, and which may al&o 

 be found in the Philosophical Magazine for .July last. — I quote a 

 few lines from that paper on the subject: " When indeed a strong 

 current of coal-gas is driven from a blowpipe so as to make 

 wire-gauze of G76 apertures strongly red hot in the atmosphere, 

 the flame from this pipe may be passed through it whilst it is 

 strongly red hot ; but this is owing to the power which wires 

 strongly ignited possess of inflaming coal-gas. and they have no 

 such effect on genuine fire-damp; and a stream of gas burning 

 in the atmosphere acting on a small quantity of matter, is en- 

 tirely different from an explosive mixture, winch is unifonu 

 within the lamp." 



But the more serious charges against the lamp are the ex- 

 plosions likely to be occasioned by the fine coal-dust, &c. floating 

 in the atmosphere of the mine ; for against this evil, no caution 

 could provide a remedy ; whereas, from what has been stated, it 

 Js evident, that most extraordinary carelessness nmst co-operate 

 with most extraordinary circumstances, to make an explosion 

 possible frou) the mere flame of the fire-damp burning in the 

 lamp. We must therefore" incjuire how correct the experi- 

 ments of Mr. Holmes arc j and we shall see presently, that 



when 



