1881.] Solar Physics Committee on Sun-Spot Observations. 157 



seen in spots are different from those most frequently seen in flames, 

 whilst in cobalt, chromium, and calcium the lines seen in spots are the 

 same as those seen in flames. 



10. Towards the end of the first series a few lines appeared among 

 the most widened ones which are not represented, so far as is known, 

 among the lines seen in the spectra of terrestrial elements. This 

 change took place when there was a marked increase in the solar 

 activity. 



So much for the results from the first series of observations. 



The second series began on 29th September, 1880, and comes down 

 •to October, 1881. From a partial reduction of the observations the 

 following results have been obtained : — 



11. The number of new lines seen amongst the most widened lines 

 has been steadily increasing. Many of these lines are very faint in 



o 



the solar spectrum, and are unrecorded by Angstrom, while they are 

 wide and dark in the spot-spectrum. 



-12. In the months of May and June of this year (1881), there was 

 ■a great change in the spectra of the spots, the old lines dying out and 

 •new lines appearing. 



13. When series of observations, consisting of ten consecutive 

 observations of the spectra of spots, taken from the commencement of 

 the first series in November, 1879, and from the end of it on 27th 

 September, 1880, were compared with those made towards the end of 

 the second series on 18th July, 1881, it was found that the lines 

 widened in each set were markedly distinct from those in the other 

 sets. 



To illustrate this, I have prepared the diagram opposite. At the 

 top are some of the principal Fraunhoferic lines in the region F to D, 

 the lengths representing the intensities. The lower part of the 

 diagram is divided into three sections by strong lines; the first of 

 these (1 — 10) contains the observations made between November 12, 

 1879, and January 20, 1880, the second (11 — 20) the observations 

 made between September 27 and October 1, 1880, and the third those 

 made between July 18 and July 29, 1881.* 



* The dates of the observations and the Greenwich liuniberhigs are as follows : — 



No. Date. Greenwich No. 



1 November 12, 1879 



2 „ 13, „ 



3 „ 14, „ 



4 „ 27, „ 



5 „ 28, „ 



6 January 3, 1880 



7 „ 12, „ ........ 301 



