DAVY. 119 



ments made for the purpose of ascertaining how the 

 inflammation takes place, that the flames will not pass 

 through tubes of a certain length or smallness of bore. 

 He then found that if the length be diminished, and the 

 bore also reduced, the flames will not pass; and he fur- 

 ther found that by multiplying the number of the tubes, 

 their length may safely be diminished to hardly any- 

 thing, provided their bore be proportionably lessened. 

 Hence it appeared that gauze of wire, whose meshes 

 were only one twenty-second of an inch diameter, stop- 

 ped the flame, and prevented the explosion. The candle 

 or lamp being wrapt in such gauze, and all access to 

 the external air prevented except through the meshes, 

 it is found that the lamp may be safely introduced into 

 a gallery filled with fire-damp ; a feeble blue flame will 

 take place inside the gauze, but no explosion, even if 

 the wire be heated nearly red. 



The theory is, but it seems very questionable, that the 

 conducting power of the wire carrying off the heat pre- 

 vents a sufficient quantity reaching the explosive com- 

 pound. Subsequent inquiries seem to prove that al- 

 though in a still atmosphere of explosive gas the lamp 

 is a perfect protection, yet it does not prevent a cur- 

 rent of gas from penetrating to the flame and exploding. 

 It is attempted to guard against this by interposing a 

 tin shield or screen; but a current very often in mining 

 operations arises before any notice can be given. Had 

 Davy's life and health been prolonged, he might^ have 

 further improved his invention so as to meet this ob- 

 jection. He certainly never was fully convinced of its 

 force, as I know from having discussed the subject 

 with him ; and no doubt the testimony of so great an 

 engineer as the late Mr. Buddie, given before a Par- 

 liamentary Committee to whom the examination of this 

 important subject was referred, deserves great attention. 

 He positively affirmed that " having seen 1000, and 

 sometimes 1500 safety-lamps in daily use, and in all 

 possible varieties of explosive mixtures, he had never 



