368 DR. C. CHREE: ANALYSIS OF RESULTS FROM THE KEW MAGNETOGRAPHS 
Inclination. 
§ 23. The most distinct phenomenon in the diurnal inequality (see Table XII. and 
fig. 3) is the maximum between 9 and 11 a.m., its occurrence being earlier in summer 
than in winter. It is difficult to speak with certainty as to the number of maxima 
and minima in several months. In the 5 months April to August, there appears to 
be only one maximum and minimum, the latter occurring between 7 and 9 p.m. 
In juost of the other months there are at least two distinct maxima and minima, 
and sometimes suggestions of a third pair (see fig. 3). In the six months October 
to March, the principal minimum of the day is found in the morning between 
5 and 7 a.m. 
In the late evening the value is so nearly stationary in most months, that a very 
long series of observations might be necessary to elucidate the exact details. 
The mean inequality for the year shows clearly only one maximum (at 10 a.m.), 
and one minimum (at 7 P.M.) ; but from 1 to 5 a.m. the value is practically 
stationary. 
As regards the range, the phenomena are similar to those noted in the declination, 
but the existence of two maxima in summer with an intervenina- minimum is far 
from clearly shown. The minimum in December is very strongly marked. 
The sum of the 24 differences also shows the December minimum clearly, but the 
value increases uniformly, though slightly from May to August. 
Horizontal Force. 
§ 24. Here two distinct maxima and minima appear in the 6 winter months, 
October to March, but only one is clearly shown in the summer months. In the 
mean inequality for the year two maxima and minima are distinctly recognisable. 
Of the turning points the forenoon minimum is the best marked [cf. fig. 4). Its 
time of occurrence varies only from about 10 to 11 a.m., being earlier in summer than 
in winter. The afternoon maximum is less prominent, especially in winter, but is on 
the whole fairly definite. In summer and at midwinter it appears about 7 p.m., but 
in some of the equinoctial and winter months it is an hour, or even two, later. 
The range and the sum of the 24 hourly differences from the mean both show a 
conspicuous minimum in December. In the 4 midsummer months it is now the sum 
of the 24 differences that shows two maxima and an intermediate badly-defined 
minimum. The range shows only one maximum, in June. The variation, however, 
in both cases is so small, from May to August, that the exact nature of the phenomena 
remains open to doubt. 
Vertical Force. 
§ 25. Here the principal minimum presents itself in the late forenoon. In the 
summer months the smallest hourly value usually occurs at noon; in the winter 
months it occurs earlier, usually at 11. 
