190 On Sir H. Davy's Safe-lamp for Mines. 



hisignificance and be forgotten, had I not found the subject pur- 

 sued in a letter from a Mr. Holmes, hi the succeeding number 

 of the same publication. The avowed intention of the author 

 of this paper, and the experiments on which he pretends to 

 ground his objections, seem to me to require some animadver- 

 sion, not indeed from the liixnahty of the former, nor the re- 

 liance (as I shall show presently) that is to be placed on the fi- 

 delity of the latter, or the inferences deduced from them; but 

 from the poss'ibUily that, if they pass altogether unnoticed, an 

 opinion may prevail, among those who have not sufficiently con- 

 sidered tlie subject, that they are founded in truth. As the re- 

 sults of Mr. Holmes's experiments are diametrically the reverse 

 of similar ones by Sir Huninhrv himself, I thought it right in 

 the first place to examine their accuracy; and with that view I 

 submitted the safe-lamp to the most rigorous trials, and under 

 circumstances as analogous to those which prevail in the coal- 

 mines as I could devise. For this purpose, I caused a cylinder 

 of strong tin plate to be constructed fourteen inches in length 

 and five in diameter, having four tubes in the bottom half an 

 inch wide, and one inch long each, placed two and two opposite 

 one another and one inch from the circumference ; aud three 

 other pairs of similar size, fixed in the sides of the cylinder, each 

 tube on the same level being opposite to its fellow. The lowest 

 pair were three inches from the bottom, the middle six, and 

 the upper pair nine inches distant from the same point. By 

 means of tliese tubes. I could expose the lamp to atmospheres of 

 various degrees of inilannnability, and I could also force the gas 

 into the cylinder with greater or less violence, and at diiferent 

 heights, from bladders connected with stop-cocks, as well as 

 project into it such substances, in fine powder, either above, be- 

 low, or on a level with the flame of the lamp, as might be thought 

 likelv to communicate explosions, through the wire-gauze, to 

 the atmosphere surrounding it ; — and I could distinctly observe 

 the phenomena through small squares of glass fixed in the sides, 

 so as to afford a full view of what passed in the interior of the 

 lanthorn. Not having any of the real fire-damp of tb.c mines, 

 I substituted for it the more inflamma'jle gas obtained from the 

 distillation of coal, and conse(iuently the trials of the safety of 

 the instrunr.ent became so much the more severe. The lamp I 

 emploved was made by Mr. Newman of Lisle-street. It is liiue 

 inches high, and the gauze cylinder, which is constructed ot 

 simple iron wire, is If inch in diameter — the diameter of the 

 v;ire being -j^'^d of an inch, and the aj)ertures, of v.-hich there are 

 060 to the square inch, -j-Vth. This lamp gives an excellent 

 light with spermaceti oil, which contimiey undiminished many 

 hours.— I will first briefly mention Mr. Holmes's experiments, 



and 



