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XVITI.— PHOTOGKAPHIC SPECTRUM OF COMET, by 

 WILLIAM HUG GINS, d.c.l., f.r.s., &c. 



[Eeceived, June 28th, 1881.] 



On Friday night (2-l;th June,) I obtrained, with one hour's exposure, 

 a photograph on a gelatine plate of the more refrangible part of 

 the spectrum of tlie Comet which is now visible. This photo- 

 graph shows a pair of bright lines a little way beyond H in the 

 ultra-violet region, approximate wave length, 3870-o890, which 

 appear to belong to the spectrum of carbon (in some form), 

 which I observed in the visible region of the spectra of telescopic 

 comets in 1866 and 1868. There is also in the photograph a 

 continuous spectrum in which the Fraunhofer lines can be seen. 

 These show that this part of the Comet's light was reflected solar 

 light. This photographic evidence supports the results I obtained 

 in 1868, which show that comets shine partly by reflected light, 

 and partly by their own light, the spectrum of which indicates 

 the presence in the Comet of carbon, possibly in combination 

 with hydrogen. 



