96 Scientific Proceedings, Royal Diibliii Society. 



M. Cornu has succeeded in photographing the solar spectrum as 

 far as a line called W (wave-length = 294-84). The photo- 

 graphs were executed with bromo-iodized collodion and ferrous 

 sulphate " developer. Comparing the spectrum with that of the 

 solar rays, it was found that the incandescence of the metal caused 

 by the action of fifty-five Bunsen's elements was much more 

 intense than sunlight. The lines in the spectrum thus observed 

 were for the most part coincident with the solar rays L, M, N, 0, 

 P) Q> Sy, T, and U, their identity was easily recognised. The 

 ray E, is due to calcium, while other important lines belong to 

 nickel, aluminium, magnesium and titanium. 



M. Cornu ascertained the wave-length of the iron lines and 

 lines in the solar spectrum by taking photographs with a Nobert's 

 grating ruled on quartz. 



In the year ] 872, 1 was engaged in making observations on the 

 absorption spectra of saline solutions with a view to elucidating 

 the nature of their constitution. — (Proceedings of the Koyal 

 Society, vol. xxii., p. 241. Proceedings of the Royal Institution. 

 On the action of Heat on Coloured Liquids. A Friday Evening 

 Lecture, April, 1875.) 



I was then led to the examination of colourless solutions in the 

 manner described by Miller. The original apparatus used by 

 him was reconstructed and the best means of obtaining good 

 results was the subject altogether of several years investigation 

 Various difiiculties and interruptions prevented a definite line of 

 research being commenced until the close of the year 1877. 



At this time I devised a method of photographing the ultra- 

 violet spectra of metals, including on one plate, accurately 

 focussed and sharp impressions of all lines lying between the 

 least and the most refrangible rays capable of acting on bromide 

 of silver. The photographs of Dr. Miller which are the only 

 spectra of the ultra-violet region that have hitherto been 

 published were executed with too wide a slit and are defective 

 in being almost entirely out of focus.* 



* I am not unmindful of the fact that Mr. Norman Lockyer on January 7th, 1875 

 (Proceedings of the Royal Society), described a new map of the solar spectrum, which he 

 ■was preparing by the aid of enlarged photographs, nor that Mr. Kand Capron has pub- 

 lished a number of excellent photographs of metallic spectra, but in neither case are rays 

 included with a greater refrangibility than X =^ 390. — (Photograplied Spectra, by J. 

 Rand Capron f.e.a.s., Spon. & Co., London). Lockyer, Phil. Trans., Vol. 1G4, pp. 484, 

 805, 1874. 



