Observations of Sun-spot Spectra, 18791894. 199 



Etheridge, R., Jim., and Jack, R. L. Catalogue of Works, Papers, 

 Reports, and Maps on the Geology, Palaeontology, Mineralogy, 

 Mining, and Metallurgy, &c., of the Australian Continent and 

 Tasmania. 8vo. London 1891. Prof. Trail, F.R.S. 



Gowers (W. R.), F.R.S. The Dynamics of Life : an Address de- 

 livered before the Medical Society of Manchester. 8vo. London 

 1894. The Author. 



"Observations of Sun-spot Spectra, 18791894." By J. 

 NORMAN LOCKYER, C.B., F.R.S. Received November 15, 

 Read November 22, 1894. 



I. The Widening of Iron Lines and of Unknown Lines in relation to the 



Sun-spot Period. 



It is now twenty-eight years since I discovered that the lines seen 

 in sun-spots were subject to widening,* and that different lines were 

 widened at different times. 



It was not, however, till 1879 that I was enabled to commence 

 daily routine work of such a nature that all observations were com- 

 parable inter se. This desideratum was secured by limiting attention 

 to the twelve lines most widened between F and D. 



In 1886f I gave an account of some of the early results obtained by 

 this research. I have recently commenced the complete discussion 

 of the whole series of observations to the present year. 



This discussion, involving 21,000 lines widened during the period 

 in question, has necessitated three special researches : the first, deal- 

 ing with the lines with which, contemporaneously, coincidences have 

 been found in the laboratory ; the second, dealing with those the 

 origin of which is so far unknown ; and the third, with the distribu- 

 tion of both sets of lines in spots in relation to the sun-spot period. 



To make the work as definite as possible, I am, in the first instance, 

 confining the inquiry concerning the known lines to lines of iron 

 based upon the examination of the pure electrolytic iron referred to 

 in a previous communication. J 



The following statistics will show the relation of these iron lines 

 to the Fraunhofer lines in the region F D over which the spot work 

 extends. In the table, " terrestrial line " means a line which has 

 been photographically recorded by myself or my assistants in the 

 spectrum of some metal or another during the past twenty-four 



* ' Roy. Soc. Proc./ vol. 15, p. 256, 1866. 

 t Ibid., vol. 40, p. 3A7. 

 J Ibid., vol. 54, p. 359. 



