204 THE SUN-SPOTS OF THE PAST FEW YEA US. 



The following paper was also read : 



THE SUN-SPOTS OF THE PAST FEW YEAES. 



BY MISS MARY WHITNEY. 



Since 1874 photographs of the sun have been taken at 

 the observatory of Vassar College, on pleasant noons 

 during college session, with considerable regularity. 

 For the past two years a daily record has also been kept 

 of the number of spots on the sun's surface. This 

 record was introduced to supplement the sun photo- 

 graphs, since the photographs are not large enough to 

 give the smallest spots or the finer details ; also, because 

 the past three years have been of unusual interest as 

 containing the epoch of maximum spot development. 

 Occasionally, also, when a striking group has presented 

 itself, drawings have been made of certain portions of 

 especial prominence. 



The most remarkable single display which I have 

 noted since March, 1883, occurred in July, 1883. I have 

 seen larger spots and more remarkable groups, but never 

 such a striking combination. Eight groups, containing 

 sixty-two spots, stretched across the sun's disc from one 

 limb to the other. This number was counted with a 

 three-inch object-glass and power of thirty diameters. 

 The arrangement was a striking one, as they lay nearly 

 in the same parallel of heliocentric latitude, giving the 

 appearance of a belt, and quite near to the equator. 

 This belt arrangement I have noticed once since (April 

 23, 1884). 



I have represented one of the eight groups as seen on 

 three successive days, and I will give, in connection, 

 some of the physical features of spots in general. 



Firstly, I may mention that spots do not appear instan- 

 taneously, although the process is sometimes very rapid. 

 In a telescope of sufficient power the phenomenon is 



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