4-JO 
DR. C. CHREE: ANALYSIS OF RESULTS FROM THE KEW MAGNETOGRAPHS 
§ 53. As ill Table XL., the yearly and seasonal values of a and h given in 
Table XLl. represent simply arithmetic means of the values for the individual 
months, and the values assigned to h/a are obtained liy comliining the h for the 
season witli the mean a. The units employed are, as in Table XL., 1' for D, and 
ly for II. 
In comparing Tallies XL. and XLI., it should be remembered that the ranges in 
the former are derived from five days in one year, while in the latter they are derived 
from a group of years supplying at least 15 days. This implies, as already pointed 
out, that the average range dealt with in Table XL. is larger than the average range 
dealt with in Table XLL 
It will be observed that the yearly and seasonal values of a” given in Table XL., 
are invariably larger than those given in Table XLI., and the same is true of the 
great majority of individual months. On the other hand the yearly and seasonal 
values of h, given for 1) and H, in Table XL., are, witli one exception, less than the 
corresponding values given in Talde XLI. A tliird point of difterence is, that the 
ecpimoctial values of h for the ranges in Table XLl. have not the pre-eminence 
compared to the summer values that they show in tlie corresponding cases in 
44ib)le XL. 
Whilst minor differences exist, tlie mam features in Jables XL. and XLI. are alike. 
Both sliow, in winter, a conspicuous minimum in 5, but a conspicuous maximum in 
5/rt. Both make the eipilnoctlal values of hja nearly equal to the mean values for 
the year. The values found for h and hja, in individual months, are evidently 
affected by considerable uncertainties, but the modes of annual variation in the two 
tallies resemble one another more closely than I had anticipated. 
It will be noticed that the values found for hja for tlie sum of the J4 hourly 
differences in Talile XLL exceed the corresponding values for tlie ranges in every 
single case in H, and in all but two individual months in L). Tliis difterence between 
the two sets of values of hja is very decidedly larger in winter than in summer. 
The inference is that sun-spot influence on Terrestrial Magnetism is really under¬ 
estimated if we confine our attention to the vcin(je of the diurnal inequalities, and 
this is especially true of winter. 
The phenomena, one need hardly say, alisoliitely bear out the remarks made in 
§ 45 as to the flat-topped character of the difference curves in figs. 18 and 19. 
§ 54. The method on which Talile XLI. is based, has also been applied to the “c” 
Fourier coefficients in tlie diurnal inequalities. The results thus obtained from the 
mean annual and seasonal inequalities for the three groups of years are given in 
Table XLII. Yearly data are given for N and W, as well as for D and H. 
For comparison, yearly results are also given for Wilhehnshaven, based on tables 
of values of the c coefficients for individual years, from 1889 to 1895, published by 
Dr. Borgen."^ I have employed 1892 to 1895 for the group of sun-spot maximum 
* ‘Beob, aus clem Magn. Obs. zu Wilhelmshaven,’ Fiinftor Theil, pp. 40 ef st>q. 
