BETWEEN SUN-SPOT FREQUENCY AND TERRESTRIAL MAGNETISM. 177 



values of a, however, so much exceed the Kew that b/a is more than twice as big at 

 Kew as it is at Batavia. 



In H the Batavia values of b are both roughly 50 per cent, in excess of the Kew, 

 but the Kew values of b/a are more than 50 per cent, in excess of those at Batavia. 



In V the values of b are again very much larger at Batavia than at Kew ; in the 

 24 diiferences the Batavia value of b/a is somewhat the higher, but in the ranges it is 

 slightly the lower. 



30. The relation between the values found for b/a is probably the best measure of 

 the relative importance of the sun-spot connection in any two cases. Applying this 

 criterion to the 24 differences and range results obtained by least squares 

 Tables XIX., we obtain the following values for the ratio of 



(b/a) from sum of 24 differences : (b/a) from ranges : 



in 



The mean of the first four of these ratios is 1'18 and the corresponding figure for 

 Kew (as deducible from (A), Table XLIV.) is 1'19. Thus the greater variability of 

 the sum of the 24 differences with sun-spot frequency observed at Kew is also seen 

 at Batavia, and to approximately the same extent. 



31. The Batavia publications record the values of the constants in the 24-hour 

 and 12-hour terms of the Fourier series 



j sin (t 



c., sin (2t + 2 ) 



for the mean diurnal inequality for the year. Here c lt c 2 replace the Batavia notation 

 A I; A 2 . 



Table XX. gives the values which I have found for a, b and b/a in this case from 

 the method of groups. The results should be compared with those given for Kew 

 and Wilhelmshaven in (A), Table XLII., though the slight difference in the method 

 of obtaining the Kew results should be noted. 



In I, H and V the values of b/a in Table XX. are nearly alike in c and c.,, and 

 they approach fairly closely to the corresponding values in Table XIX. applicable to 

 the ranges of the mean diurnal inequalities. In declination and total force, however, 

 the values of b/a in Table XX. are decidedly higher for c x than for c 3 . This 

 phenomenon was observed at both Kew and Wilhelmshaven in the case of the 

 declination and the westerly component. 



VOL. coin. A 



2 A 



