452 



Sir J. Norman Lockyer. 



spectrum and the solar spectrum taken at Kensington, the siliciune 

 line apparently agrees better in position with the less refrangible edge 

 of the solar line than with the middle. 



Before this point can be definitely settled, still larger dispersion will 

 have to be employed. 



In the paper mentioned, it was shown that silicium made its appear- 

 ance first at the temperature represented by a Ursse Minoris, and 

 strengthened at the higher temperature of ol Cygni and /3 Orionis, 

 afterwards weakening as we pass through the still higher temperatures 

 of C Tauri and y Orionis, until at the ( Orionis stage it is bordering on 

 extinction. 



In the same paper the behaviour of a line at A 4089-2 was plotted, 

 and at the same time it was quoted as an " unknown ; ' line. 



It is interesting to note that this line is now traced to silicium, and 

 is the strongest line in set B. It is apparently a short-lived line in 

 stellar spectra, as it only occurs between the stages of temperature 

 represented by y Orionis and £ Orionis, being one of the weakest lines 

 in the spectrum of the former star, and one of the strongest in that of 

 the latter. 



Most of the photographs of the silicium spectrum under varying 

 conditions were taken by Mr. Butler. The wave-lengths of the lines 

 have been reduced by Mr. Baxandall, and he is also responsible for 

 establishing the identity of the terrestrial and the stellar lines. My 

 thanks are due to him also for help in the preparation of the present 

 communication. 



Preliminary Table of Wave-lengths of Enhanced Lines." By 

 Sir Noemax Lockyee, K.C.B., E.B.S. Received November 9 r 

 —Bead November 23, 1899. 



Introduction. 



In the year 1881 I communicated a paper* to the Boyal Society in 

 which I described some experiments relating to the brightening of some 

 lines in the spectrum of iron on passing from the arc to the spark. 



It was found that in the case of iron, the two lines in the visible 

 spectrum at X 4924*1 and A5018 - 6, on Rowland's scale, were greatly 

 enhanced in brightness, and were very important in solar phenomena. 



The work was subsequently carried into the photographic region of 

 the spectrum with very interesting results, since it was found that 

 several other lines were enhanced at the highest temperature I could 

 then obtain. 



In a later paperf I described the results obtained in further photo- 



* 1 Roy. Soc. Proc.,' 1881, vol. 32, p. 204. 

 f < Roy. Soc. Proc.,' vol. 61, p. 158. 



