130 tSioux City Academy of Science and Letters. 



ing of lines, darkening of lines without widening, 

 displacement of lines, obliteration of lines across spots, 

 reversal of lines, liazy fringes to lines and spot bands. 

 He found the D lines of Sodium reversed and displaced, 

 the Ha line of Hydrogen rarely widened, but frequentl}^ 

 reversed, twisted and displaced. The lines due to the 

 ■elements Vanadium, Chromium, Sodium, Titanium, Cal- 

 cium, Cobalt, Nickel, Oxygen, Manganese and Iron were 

 mainly involved in the spectra of the sunspots examined. 

 The spectrum of sunspots appears to undergo decided 

 changes at the epochs of maximum and minimum sun- 

 spot frequency; the lines most widened near the mini- 

 mum period being mainly the known lines of the metals, 

 whereas those affected near the maximum belong to the 

 unknown class. 



Frequently sunspots exhibit evidence of violent 

 agitation of the gases overlying the disturbed region by 

 reversals, displacements and distortions of lines; the 

 hydrogen, helium and calcium lines are those principally 

 affected, although double reversals are sometimes de- 

 tected in the sodium and magnesium lines. 



Occasionally the eruptions in active spots are so 

 striking and brilliant that the forms of the gaseous 

 masses can be clearly seen with the spectroscope. 

 Several of these occurrences have come under the 

 writer's notice; one in particular accompanied the enor- 

 mous group visible in the month of September, 1898. 

 This disturbance was remarkable for the various mag- 

 netic and electrical manifestations which accompanied 

 it on the 7th. As the group was nearing the central 

 meridian the entire region in the vicinity of the group 

 was violently agitated, the hydrogen line was reversed 

 and distorted in all directions, and upon opening the 

 slit of the spectroscope the flame and spike-like form of 

 the incandescent clouds was clearly seen extending 

 from the umbra to the edge of the iDenumbra on the east 

 edge; the D3 line of helium was also bright and the 

 sodium D lines and others widened. Such outbursts 

 as these are probably identical with the metallic 

 protuberances seen at the edge of the disc, but which 

 cannot be so readily observed on the more brilliant 

 background of the solar surface. The very complex 



