354 DR. C. CHREE; ANALYSIS OF RESULTS FROM THE KFAY MAGNETOGRAPHS 
the daily change which we have to account for really amounts on the average of 
the eleven years to 0''044 + O'^OIG or 0'’06. Again, the annual inequalitv is in 
general such as to diminish the numerical values found for the non-cvclic effect. In 
fact we see from Tables lY". and Y". that the non-cyclic effect is positive in Ylarch and 
April, the montlis in which the annual inecpiality is changing fastest from positive to 
negative, while it is negative in July and August, months in which the annual 
inerpiality is clianging from negative to positive. 
This brings us to another suggestive feature. Four of the fii'e months in which 
the mean non-cyclic effect is negative are summer months, while it is positive in six 
successive months, November to April, including all the mid-winter months. Then, 
as regards differences of sign in different years, sun-spots were exceptionallv few in 
1890, and though fairly numerous were rapidly diminishing in 1895, 1896, and 1897, 
the otlier three vears in which the mean non-cvclic effect was negative. On the other 
hand, 1891 to 1894, the years in which the non-cyclic effect has its largest positive 
values, were years in which sun-spots were either very numerous or increasing rapidly 
in number. Thus I tliink that whilst it would be unwise to dogmatise as to the cause 
of the apparent non-cyclic effect in D, the evidence distinctly points to the conclusion 
that it is a true magnetic |ihenomenon which varies, however, with the season of the 
year, and with the position of the year in the sun-spot cycle. 
§ 16. In the case of I (see Table YN.), the non-cyclic effect is evidently no chance 
phenomenon. The means for every year of the eleven, and for everv month of the 
twelve, alike come out negative, and the preponderance of individual months in which 
the effect is negative is overwhelming. The true secular change is here in the same 
direction as the apparent noTi-cyclic effect, and so tends to increase it, but onJv to an 
insignificant extent. In fact it requires only 10 average quiet days to bring about a 
decrease in I equal to the secular change observed in an entire vear. 
The absolute magnitude of the non-cyclic change in I, as we see from Table X., 
does not vary very conspicuously with the season of the year, but relative to the 
range of the diurnal inequality it is most important in winter. In January, in fact, it 
averaged fully 30 per cent, of the range of the proper cyclic diurnal variation. 
§ 17. The non-cyclic effect in H, see Table VII., is as prominent as in I. Here also 
it is increased by the contribution from the secular change, but 8 average quiet davs 
suffice to produce an increment in the force equal to the full secular change for the 
year. The non-cyclic effect in H is on the whole wonderfully uniform throughout 
the year, but it appears somewhat reduced at midsummer. Relative to the range 
of the diurnal inequality, it is most important in winter ; in January, in fact, it 
averaged over 20 per cent, of the observed range. 
In V , see Table Y'lIL, the non-cyclic effect is considerablv less conspicuous than 
in H or I, but more consjiicuous than in D. There is a decided preponderance 
of months in which it has the negative sign, and the mean annual value is positive 
in only 2 out of the 11 years. According to. Table X., the magnitude of tlie non- 
