33G DE. C. CHREE: ANALYSIS OF RESULTS FROM THE KEW MAGNETOGRAPHS 
selected quiet days have Ijeeu published annually in the ‘ Report ’ made to the Royal 
Society. 
In 1895 I contributed to the British Association ‘Report’ an analysis of the 
declination and horizontal force records for the years 1890 to 1894, and described 
the previously unnoticed “ non-cyclic effects ” which appear to be characteristic of 
magnetically quiet days at Kew and elsewhere. In 1901 the development of electric 
traction in the West of London rendered it clear that no further records at Kew 
would be free from suspicion of artificial disturbances, and that it would be necessary 
in the near future to make arrangements for continuing the magnetic work elsewhere. 
Both contingencies pointed to the expediency of a complete discussion of the data 
obtained from 1890 to 1900, which I accordingly commenced. The delay in the 
execution of the scheme is largely due to the occurrence of various unforeseen 
difficulties, which have, however, I think been at last fairly satisfactorily surmounted. 
The object of the paper is not so much to put observations on record, as to make a 
critical use of them. The data used are mainly derived from old Kew ‘ Reports,’ to 
which reference must be made for particulars. 
§ 2. One of the questions dealt with is the relation between sun-spots and terrestrial 
magnetism. The sun-spot data made use of are from the very important table 
published by Wolfee, in the ‘Met. Zeit.’"^ Wolfer’s table gives the mean monthly 
values assigned to the sun-spot frec|uency by Wolf and Wolfer for a verv long 
series of years. As frequent reference has to be made to sun-spot data throughout 
the whole of this paper, it is convenient to reproduce at once that part of Wolfer’s 
table which applies to the period 1890 to 1900 now under review. This will be found 
in Table I. In addition to Wolfer’s own figures I give the mean sun-spot frequency 
obtained for each month of the year when we combine the 11 years 1890 to 1900. 
It Vvill be noticed that the four years 1892 to 1895 are conspicuously years of sun¬ 
spot maximum, while 1890, 1899, and 1900 are years of very few sun-spots. The 
mean frec|uency for the 12 months commencing August, 1893, and ending July, 1894, 
is higher than for any other 12 successive months in the 11-year period. Con¬ 
sidering that so many as 11 years are included, the irregularity in the mean values 
for the several months of the year is rather surprising. March and November in 
particular show a remarkably low mean frequency. This is to l)e regretted, as it 
introduces a certain element of uncertainty into some of the calculations made in the 
latter part of the paper. 
* 
May, 1902, p. 193, et seq. 
