384 DR. C. CHREE: ANALYSTS OF RESULTS FROM THE FALIUOTTTH MAGNETO- 



5. It is natural to suppose as was in fact remarked by myself when first 

 discussing the phenomenon* that the non -cyclic increase in H on quiet days is 

 connected in some way with the considerable decrements in H, which in the majority 

 of instances accompany magnetic storms. It would appear, however, that the 

 mean size of the non-cyclic effect on the Astronomer Royal's quiet days for a year 

 cannot be inferred from the character of that year as disturbed or otherwise. For 

 example, 1894 was much more disturbed than the years immediately preceding or 

 following it ; but the mean non-cyclic effect in H at both Kew and Falmouth is 

 distinctly less for 1894 than for 1893 or 1895. There were, in fact, only 4 months 

 out of the 12 in which the non-cyclic effect in 1894 exceeded that in 1895, and only 

 2 months in which it exceeded that in 1893. Again, during the four sun-spot 

 minimum years, 1899 to 1902, few months showed anything that would be classified 

 as a magnetic storm in years of sun-spot maximum, and yet the proportion of months 

 showing a decidedly positive non-cyclic effect is the same as for the disturbed 

 year 1894. 



Solar Diurnal Inequality. 



6. The diurnal inequality figures in the annual Falmouth Reports include the 

 non-cyclic effect. This has been eliminated in preparing Tables V. and VI. in the 

 way described in (A) 18. The hours, it is important to notice, are Greenwich mean 

 time. Values of N and W are not given in the Falmouth Tables. The hourly values 

 in Tables VII. and VIII. were deduced from those in Tables V. and VI. by means of 

 the relations the units being ly and 1' 



8N = 0-947SH-1741SD, 

 SW = 0-3228H+5-128D, 



these being the special forms taken by the general formulae 



SN = cosD8H-HsinD8D, 

 SW = sin D8H+H cos DSD, 



when D and H are assigned the mean values at the foot of Table I. 



As in (A), D and W are counted positively to the west, and to avoid decimals the 

 unit of force employed in the tables is y/10. In reality D is measured only to O''l, 

 and H to ly, so the tables go a figure beyond the observations. This is completely 

 justified so far as Tables V. to VIII. are concerned, because the figures assigned to 

 any one month are means from 12 years, and the yearly means for the two sun-spot 

 periods are baaed each on 48 months. 



In addition to the mean hourly values, the tables give the range (defined as the 



* 'B. A. Report for 1895,' p. 212. 



