126 On the E^eci of swTOtinding Media on Voltaic Ignition. 



The differences of effect of all gases other than hydrogen and 

 such compounds are quite insignificant when compared with 

 the differences between the hydrogenous and the other gases. 

 There are some phaenomena which I have before observed, 

 and which were, at the time I noticed them, inexplicable to 

 me; but they now appear dependent on this physical pecu- 

 liarity of hydrogen. Thus, if a jet of oxygen gas be kindled 

 in an atmosphere of carburetted hydrogen, the flame is smaller 

 than when the converse effect takes place. The voltaic arc 

 between metallic terminals is also much smaller in hydrogen 

 gas than in nitrogen, though both these gases are incapable of 

 combining with the terminals; indeed to obtain an arc at all 

 in hydrogen is scarcely practicable. 



Davy has, in his Researches on Flame, given several expe- 

 riments which are similarly explicable; but though noting the 

 results, he nowhere, as far as I am aware, attributes them to 

 any specific peculiarity of hydrogen. 



Of the phaenomenon which I have examined in this paper, 

 I first published an account in connexion with some experi- 

 ments on the application of voltaic ignition to lighting mines, 

 and it does not appear impossible that the experiments now 

 detailed may ultimately find some beneficial application in 

 solving the problem of a safety-light for mines. A light which 

 is just able to support itself under the cooling effect of ordi- 

 nary atmospheric air would be extinguished by air mixed with 

 hydrogenous gas. 



I am far from pretending to have devised any means of ful- 

 filling these conditions, and yet supplying an efficient light; 

 I merely throw it out as a suggestion for consideration, know- 

 ing that there are no additions to our knowledge which are 

 not ultimately valuable in their practical application; and 

 that a suggestion, however vague, — a new point to those whose 

 minds may be occupied with the subject, may lead them to 

 results which he who makes the suggestion is unable to attain. 



P.S. Since this paper was communicated I have received a 

 paper from Dr. Andrews of Belfast, who published as early 

 as 1840, in the Proceedings of the Royal Irish Academy, ex- 

 periments similar to those of mine first puV)lished in 1845. 

 My experiments were made in the same year as those of Dr. 

 Andrews, but as 1 withheld their publication, Dr. Andrews is 

 fully entitled to priority. Had I known of his experiments 

 earlier, I should have recited them in the first part of this 

 paper. 



