[ 75 ] 
III. Some Phenomena of Sunspots and of Terrestrial Magnetism at Kew 
Observatory. 
By C. Chkee, Sc.D., LL.D., F.R.S., Superintefidefit of Kew Observatory. 
Received March 30,—Read May 9, 1912. 
Contents. 
Page 
1-6. Explanatory and historical. 75 
7. Relative advantages for the enquiry of declination and horizontal force daily ranges . 79 
8. Basis of investigation.82 
9, 10. Greenwich sunspot areas on 31 representative successive days.83 
11, 12. Kew horizontal force ranges on 31 representative successive days.86 
13. Kew mean horizontal force ranges for individual years.89 
11. Magnetic “ character ” figures discussed. 89 
15-19. „ „ ,, on 31 representative successive days.91 
20. Periods previously suggested.97 
21-25. The 27-28 day period. 98 
26-27. Effects of disturbance on phenomena observed.101 
28. Mean annual values of ranges and “ character ” figures . . . .•.110 
29. Annual variation in ranges and “ character” figures.Ill 
30, 31. Relative mean monthly values of ranges and “ character ” figures.113 
32,33. Conclusions.Ill 
§ 1. It was discovered iialf a century ago by Sabine, Lamont and Wolf that a 
relation exists between sunspots and the daily range of magnetic declination. If the 
regular diurnal inequality of declination be determined for the year as a whole, then 
it has been shown that corresponding to equal increments of sunspot frequency, as 
determined by Wolf and Wolfer, of Zurich, there are at least approximately equal 
increments in the range. In some instances the range taken has been not that of an 
inequality derived from all hours of the day, hut one derived from daily measurements 
at two fixed hours, approaching more or less closely to the average times at which 
the needle has its extreme easterly and westerly positions. The range thus derived 
is unlikely to bear an absolutely invariable ratio to the range of the diurnal 
inequality, but for the present purpose the comparison may be regarded as made 
with the range of the diurnal inequality, but of minor accuracy. 
VOL. CCXII.-A 486 . L 2 Publislied separate!}', July 10, 1913. 
