424 Mr. Murratf on the [Dec. 



Article V. 



On the Impermeahility of Wire Gauze to Flame. 

 By Mr. Murray. 



(To Dr. Thomson.) 

 SIR, 



An anonymous correspondent in your Antiah, I believe, was 

 * the first to suggest that the impermeabihty of wire gauze to flame 

 might be ascribed to its coohng influence, and it was adopted by 

 that eminent chemist. Sir H. Davy, who very laudably endea- 

 voured to prove its truth, or fallacy, by direct experiment. Now 

 I must in candour submit, with every deference to that great 

 authority, that though his conclusions may seem satisfactory to 

 his own ingenious mind, that there are not a few who cannot 

 say Amen, and of that number I am one. No persons, Sir, can 

 have a more exalted opinion of that philosopher than myself, but 

 no opinion shall pass current with me merely because it bears 

 the signet and superscription of a great name. I have atten- 

 tively considered his experiments, and repeated some of them. 



I confess that I was inclined at first to think that a solution 

 might be formed in the products of combustion. The aqueous 

 Tapour and carbonic acid which, together with the unaltered 

 azote of the atmosphere surrounding the cylinder exteriorly 

 might form, it occurred to me, a zone pervious to gaseous matter, 

 and yet impervious to flame. The iiieshes of the safety lamp 

 ■would, in like manner, be filled up with the same negative mate- 

 rials. This, however, was a mere opinion, though it seemed 

 deducible from some experiments made by me, and recorded ia 

 the pages of the Philosophical Journal. 



I would now find a solution of the question in the structure of 

 flame itself. Flame is clearly a film : this, as I have already 

 shown, may be demonstrated by pressing on the apex of a cone 

 of flame by means of a plate of glass, or sufi^ering alcohol or ether 

 to be set on fire on the same plane. But press gently on the 

 cone of flame, and it will be seen to recoil or curve downwards, 

 "whereas it should become extinct in contact with the wire gauze, 

 if a cooling influence were exerted. In like manner when we 

 incline the wire gauze laterally in the direction of any of the 

 conic sections, the film will separate, and the mantle widen and 

 elongate laterally. 



It is hence clear from the very structure of flame considered 

 as a film that it cannot pass through, even when the wire gauze 

 is ignited, because if a film were forced through, it must neces- 

 sarily become solid. We find an analogy in water placed on a 

 plane of fine wire gauze, it spreads a filmy web over the 

 meshes, and is effectually retained, but when the meshes are 



