1881.] Solar Pliysics Committee on Sun-Spot Observations. 155 



been made ; the maps for the first and second hundred observations 

 have been drawn up and the tabulation of the first hundred completed. 

 The reductions are being carried on, and I hope shortly to be able to 

 lay a full report upon the 200 observations before the Committee, but 

 desire, in the mean time, to bring the present preliminary one before 

 it. 



The reduction of the first hundred observations, extending from 

 November, 1879, to September, 1880, has yielded the following re- 

 sults : — 



1. An immense variation, from spot to spot, is to be observed 

 between the most widened lines seen in the first hundred observations. 

 Change of quantity or density w T ill not account for this variation. To 

 investigate this point I had the individual observations of lines seen 

 in the spectrum of iron plotted out on strips of paper, and I then 

 tried to arrange them in order, but I could not succeed, for even when 

 the observations were divided into six groups about half of them were 

 left outstanding. 



2. If we consider the lines of any one substance, there is as much 

 inversion between these lines as between the lines of any two metals. 

 By the term inversion I mean of any three lines A, B, C, that we may 

 get A and B without C, A and C without B, B and C without A, and 

 so on. 



3. We have reason to believe, from experiments made here, that 

 most of the lines seen in the spectrum of iron volatilised in the oxy- 

 hydrogen blowpipe flame are amongst the most widened lines. 



4. Certain lines of iron have been seen at rest, while other adjacent 

 lines seen in the spectrum of this metal in the same field of view have 

 shown change of wave-length. 



5. The spectrum of iron in the solar spectrum is more like that of 

 the arc than that of the spark. 



6. The greater part of the lines seen in spots and flames are 

 common to two or more substances with the dispersion employed. 



7. The first hundred spot observations being compared with a 

 hundred observations of the spectra of flames, made by Tacchini at 

 Palermo, have shown that there is no iron line in the region b-F 

 common to spots and prominences. 



In addition to these facts, already communicated to the Committee 

 in more or less detail at different times, the following have been 

 noticed in the continuation of the reductions. 



8. The lines of iron, cobalt, chromium, manganese, titanium, 

 calcium, and nickel seen in the spectra of spots and flames are usually 

 coincident with lines in the spectra of other metals, with the dis- 

 persion employed, whilst the lines of tungsten, copper, and zinc seen 

 in spots and storms are not coincident with lines in other spectra. 



9. The lines of iron, manganese, zinc, and titanium most frequently 



