KEACTION OP PLANETS UPON SUN PUISEUX. 167 



RESEARCHES OE MRS. MAUNDER, 19 7. 



Mrs. Maunder undertook to answer this question, utilizing the 

 photographs due to a cooperation of English observatories for the 

 interval 1889 to 1901, extending from one spot minimum to the next. 

 At the beginning and the end the sun seemed absolutely free from 

 spots. In every instance the rare survivors which could be found at 

 the beginning and the end of the period upon the visible hemisphere 

 could not vitiate the conclusions derived from all the observations. 



The tables obtained at Greenwich comprised — 



( 1 ) The positions and areas of the groups for each day. 



(2) The history, day by day, of each important group; the areas 

 are expressed in millionths of the visible hemisphere and are cor- 

 rected for the effect of perspective ; the mean duration of a group is 

 about six days ; 2,870 groups were studied. 



Mrs. Maunder divided the visible hemisphere at each instant into 

 14 vertical zones, each 13.2° wide and numbered in the inverse order 

 of their appearance. For each zone and the entire period the sum 

 representing the area of the spots was made. These results were com- 

 pared for zones symmetrical to the central meridian. There was thus 

 made manifest a systematic variation from two points of view : 



(1) Despite the perspective correction, there was a constant pro- 

 gression on each side in passing from the limb to the central zone, as 

 if the perspective correction had been insufficient. 



(2) For each pair of zones there was a constant decrease in passing 

 from the eastern to the corresponding western zone. The same thing 

 was noted when in a similar manner the northern and southern hem- 

 ispheres w^ere treated separately. 



Various reasons make the measures on the extreme zones less trust- 

 worthy, but even if we omit them the same conclusions result. If 

 refraction in the solar atmosphere plays a part it would unduly en- 

 rich the extreme zones. Accordingly, if a correction is made for it, 

 it but increases the first anomaly. Neither anomaly can be due to 

 errors of observation or reduction. 



If we do not like this process of treatment we need not depend 

 upon the areas of the spots but count simply the number of groups 

 visible in each zone, omitting those of long life which necessarily 

 appear in both halves. Here again, for all pairs of zones, the eastern 

 one shows a greater number than its corresponding western one. 



We next ask whether there is, either in the visible or in the invis- 

 ible half, an habitual and systematic excess in the number of spot 

 births over deaths. A priori, it seems as if it must be so for one or 

 the other hemisphere during the phase of increasing spots, but that 

 an equilibrium must be established when a complete cycle is con- 

 sidered. 



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