IOWA ACADEMY OF SCIENCES. 81 



formation and appearance of a sunspot. One cannot study 

 the solar surface markings day after day for years, without 

 coming to the conclusion that the mechanism of a sunspot 

 is analogous to our terrestrial cyclones and other storms, the 

 stupendous forces far below the visible photosphere mani- 

 festing the violence of their eruptions by the extent, area, 

 color and form of umbra and penumbra, and various other 

 phenomena, including that of terrestrial magnetic and 

 atmospherical electrical effects. 



The decline in total number of groups and spots was 

 quite marked during the year under review; several days 

 without spots were noted in April, August and October. 



A fine group consisting of from three to five centers of 

 activity was observed from 18th to 29th of February, in 

 north latitude. 



An interesting feature of May was the development 

 from a few dots to a group of considerable size on the visi- 

 ble disc from the 26th to 3d of June. 



A great spot which underwent many changes passed 

 across the disc from July 12th to 24th; on the 20th its area 

 was nearly 400,000,000 square miles. September brought 

 the most remarkable group of the year— a stream of spots 

 extending over 26^ of solar longitude, or about 190,000 

 miles — first observed as irregular spots near the east limb, 

 on the lOfch, and rapidly increased by the next day with 

 many nuclei; the groups increased daily until the 20th, 

 when the greatest elongation occurred; by the 22d it was 

 passing out of view round the west limb, and must have 

 rapidly declined on the invisible disc of the sun, as its 

 return during the following month was marked by only a 

 normal spot. 



A brilliant solar protuberance was witnessed on October 

 23d, at the east limb, position angle 110^, almost directly 

 over a large spot which was coming into view; it was in 

 violent agitation, but was of short duration, as the dis- 

 turbance entirely subsided in about an hour. My detailed 

 account of the phenomenon was published in Popular 

 Astronomy for December, 1896. Two days later a large 



