IOWA ACADEMY OF SCIENCES. 87 



the interum rotations; but in its place, on March 30th, a 

 bright taeniae at the east limb was coincident with an 

 unusual manifestation of the aurora— a full account of 

 which I contributed, to Popular Astyonomjj for May, 1902, 

 extracts of which are given here. "About 9 o'clock in the 

 evening of March 29th, 1902, a bright auroral beam was 

 observed in the south-east sky, at an altitude of about 30 

 degrees. When first seen it was more or less obscured by 

 light clouds, and its true nature was hard to determine. 

 It was a perpendicular, pale, narrow streak of light, about 

 5 degrees in length and about i degree in width, with the 

 star Gamma in the constellation Virgo, about exactly in the 

 middle of the beam. About twenty minutes later the clouds 

 cleared aw^ay and the beam was a beautiful object, resem- 

 bling strpngly a fine comet of a pale greenish white light. 

 Ten minutes later it reached its maximum brightness, 

 when it was a deep yellow to orange color, and had moved 

 about a degree farther north. Underneath, towards the 

 horizon, was a dark region, above which was a faint auroral 

 glow. Five minutes later the phenomenon disappeared, 

 and did not appear again. Its position in the south-east 

 sky was unusual." 



After the disappearance of the May group, the sun's 

 surface was practically spotless for a period extending over 

 four rotations. 



During the latter part of September and in October, fair 

 sized groups in south latitude, belonging to the new cycle, 

 were present. 



No disturbance of the first magnitude was visible during 

 the year. There ^vere 163 spotless days out of 230 days of 

 observation, or about seventy-one per cent, which indi- 

 cates the uncertainty and sometimes difficulty of deter- 

 mining the precise date of the minimum epoch. 



In the following tables are given the numerical summa- 

 ries of all the observations from August, 1890, to Decem- 

 ber, 1902, inclusive. The columns are self-explanatory. 



The results thus tabulated are shown graphically in 

 Plate XXIII, which exhibits the progress of the average 

 daily numbers of spot groups. 



