Thomson's Si/stem of Chemistri/. 123 



displace it. If we suppose such a fixedness to exist, it would 

 account for the explosion not kindling the surrounding mixture 

 on the outside of the sieve. This contrivance (supposing it 

 effectual) would completely answer the purpose of the miner*." 



The Doctor's insinuations and theory are of a piece. In Sir 

 H. Davy's previous paper in the Transactions, reprinted in the 

 Philosophical Magazine, for December, 1815, we find the fol- 

 lowing luminous passage : " In comparing the power of tubes of 

 metal, and those of glass, it appeared that the flame passed 

 more readily through glass tubes of the same diameter ; and that 

 explosions were stopped by metallic tubes of ^ of an inch, when 

 they were l-J- inch long ; and this phsenomenon probably de- 

 pends upon the heat lost during the explosion, in contact with 

 so great a cooling surface, which brings the temperature of the 

 first portions exploded, below that required for the firing of the 

 other portions. Metal is a better conductor of heat than glass; 

 and it has been already shewn, that the fire-damp requires a 

 very strong heat for its inflammation." So much with respect 

 to the fact being " most unaccountable" at the time when Dr. 

 Thomson wrote the above report. The absurdity of his own 

 theory will appear, from a decisive experiment in Sir H. Davy's 

 preceding paper. " But 1 was not contented with these trials, 

 and I submitted the safety canals, tubes, and wire-gauze sieves, 

 to much more severe tests ; I made them the medium of commu- 

 nication between a large glass vessel filled with the strongest 

 explosive mixture of carburetted hydrogen and air, and a bladder 

 f or i full of the same mixture, both insulated from the atmo- 

 sphere. By means of wires passing near the stop-cock of the 

 glass vessel, I fired the ex,plosive mixture in it, by the discharge 

 of a Leyden jar. The bladder always expanded at the moment 

 the explosion was made ; a contraction as rapidly took place ; 

 and a lambent flame played round the mouths of the safety 

 apertures, open in the glass vessel ; but the mixture in the blad- 

 der did not explode." Here the air was displaced, but not 

 kindled ; in direct confutation of Dr. Thomson's theory, and in 

 justification of Sir H. Davy's expression, chemical Jire-sieve. 



The pages of Dr. Thomson's- Annals became for some timie 

 tliereafter, the receptacle of much criticism, and invective, 

 against the safety-lamp and its inventor. Since that period^ 

 however, Doctor Thomson has set up as the Autocrat of 

 Chemistry, assigning to each of his cotemporaries, the rank 

 he ought to occupy, with despotic decision. Of M. Gay-Lussac, 

 he says, " We may pity the pusillanimityf ; " and he arraigns 

 M. Thenard with downright dishonesty, as we shall shew iu 

 the sequel. "Mere experimenters," says he, "may relin- 

 quish the field ; for there is not a great deal more, which they 



* /Innals of l'l,Uo»ophy,¥iih. 181C, p. 135. t l'''il- Ja>'- '816. 



