Voltaic Ignition to Lighting ^ine^ 



445 



exaltation of etFect protlucecl. The very necessity of inclosing 

 the coil in a glass recipient also augnients the heat, the light, 

 and the resistance; if I remember rightly, Mr. Faraday first 

 proposed inclosing wire in a tube for the purpose of being 

 able to ignite a longer portion of it. Lastly, only two or three 

 cells are required (one indeed might be sometimes sufficient^ 

 and the whole apparatus thus becomes portable and oecono- 

 uiical. The light is perfectly constant, subject to no fluctua- 

 tion or interruption, and the heat is not so excessive as to 

 destroy the apparatus. ^, j, „ i , ; -*. ^i i , : 



As the effect of different gases on radiant neat is an ifp- 

 portant element in the practical application of the above,''! 

 had commenced some experiments on this subject, and tlie 

 following I find in my note-book as the effect of four differ- 

 ent gases. A voltameter was interposed in the circuit in or- 

 der to furnish a better test of the amount of ignition than the 

 eye, as, according to the position of Davy, that a wire bei 

 comes a worse conductor in proportion to its increase of tem- 

 perature, the amount of gas in the voltameter should be, as 

 indeed in these experiments it turned out to be, in inverse 

 proportion to the degree of ignition. As a further test, the 

 increased volume of the gas by expansion was noted, though 

 the apparatus was not constru<fted for showing ibis increase 

 with delicate accuracy. V.,/^,f+; „ . ^, ,';+.,- 't • i ^ ' •> > . 



beJfirr 



■'}■■■ ill 

 -mao 



rlr, 



.11 



')'> 



Platina wire ignited 

 by a given 

 constant voltaic 

 battery in ' ; 



cTJr-r 



•J'.)); 



n'.'lCBecikiO'l 



0-! i^'jyU 3d 'JJiUl I 



/Not vIMfeJ^'^-te^eb 



Hydrogen--f.j^j„j|_.j„ the darki....|i jd ^J Irt 



Carbonic fi^id)o {'^^ri'lf ^^\\>^mk-^ 



wrnlfi ^uo^is:-: i daylight J 



A . '^ r i f Incandescent." by"! ^o c 



^^yS^"" :a.;.U.| daylight J/.'..(4^ f^?'^^ 



'Niftogen... ^me i...,..,i>^rt.:i i24f !o 



Atmospheric airjSHmeji.i,.<K»i-t!>*»>iv'f Xij^^luo 



Voltameter 

 gave at the 

 rate of one 

 cub. in. in 



J3 'i 



J 



n, 



Aio. 



Expansion 

 of volmne. 



lainlfiiil) ! 



■"■) 



hJeia 

 iu5 



' I had intended to have carried these experiments furtner 

 with other gases*, and also with condensed and rarefied air, 

 but was interrupted ; and as it may be some time before I may 

 be able to renew them, I think I cannot do better than sub- 

 mit these experiments, with your permission, to the readers 



,^ *'I have some doubt whether the different gases do not exercise a spe- 

 cific action on the ignited wire, somewhat in the nature of catalysis ; it' a 

 wire be brought by the voltaic current to a white heat in atmospheric air, 

 and a vessel of hydrogen inverted over it, .^|ji^..]igljijt jj^jis ^j^d(i^ly^.e^^n- 

 guished as the flame of a candle would be. -■»l i' ' .ihiofiu)v.''U v> 



