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V. Magnetic Declination at Kew Observatory , 1890 to 1900. 
By C. Chree, Sc.D., LL.D., F.R.S., Superintendent Observatory Department, 
National Physical Laboratory. 
{From the National Physical Laboratory .) 
Received November 2,—Read December 12, 1907. 
Contents. 
Sections Page 
1-2. Introductory. 205 
3-7. Disturbed days, and disturbances . 206 
8. Days excluded.210 
9. Mean annual values from ordinary and quiet days contrasted.211 
10-12. Diurnal inequality.'.212 
13-17. Diurnal inequality. Fourier coefficients.219 
18-20. Absolute ranges.225 
21. Absolute ranges. Frequency of specified amplitude.227 
22, 23. Frequency of occurrences of maxima and minima at different hours of the day .... 229 
24. Annual variation. Fourier coefficients.232 
25. Sunspot relationships.234 
26. Sunspot relationships. Occurrence of quiet and disturbed days.235 
27-30. Sunspot areas and magnetic ranges grouped and compared.237 
31. Magnetic ranges and faculse compared.242 
32. Discussion of remarkable special cases. 242 
33, 34. Applications of Wolf’s formula.245 
§ 1. In 1903 I carried out an analysis’*—referred to here for brevity as A—of the 
results given by the Kew magnetographs on “ quiet ” days during the 11 years 1890 
to 1900. This investigation brought to light various novel phenomena. It was sub¬ 
sequently shown—in a paper f to be referred to as B—that these phenomena are 
equally true of “ quiet 7 ’ days at Falmouth. Some of the phenomena suggested the 
* 1 Phil. Trans. Roy. Soc.,’ A, vol. 202, p. 335, 1903. 
t 1 Phil. Trans. Roy. Soc.,’ A, vol. 204, p. 373, 1905. 
VOL. CCVIII.—A 431. 
19.5.08 
