1904.] Sunspot Frequency and Terrestrial Magnetism. 199 



suggests, of course, that the apparent considerable variations in the 

 values of b/a just alluded to may be mainly due to observational 

 imperfections, but uncertainty is not unlikely to remain on this point 

 until the recurrence of a period of exceptionally high or low sunspot 

 frequency. 



§ 3. Table I gives some of the principal results obtained in the case 

 of the range of the mean diurnal inequality for the year. The units 

 are 1' for angles, and 0*00001 C.G.S (or 1 y) for force components. 



Table I. 



Place. 



Data 

 from — 



Declination. 



Horizontal 

 force. 



Vertical 

 force. 



a. 



10 4 Z>. 



10 4 £/a. 



a. jl0 3 5. 10 4 J/a. 



a. 



J0 3 6.|l0 4 6/a. 





All clays . . 



5'74 



400 



70 



20-7 211 



102 



8-1 



285 



326 





Quiet days 



6-l7j 424 



69 



20-6 195 



95 



59 



27 



46 



Katliarinenburg. 



Ail days'.. 



5-29, 342 



65 



16-8, 182 



109 



8-6 



117 



137 



Kew 



Quiet days 



6-10 433 



71 



18-1 194 



107 



11-3 



81 



56 





All days . . 

 jj • • 



2-471 179 



73 



387 274 



71 



30-1 



156 



52 





4-06 164 



40 



15-0 96 



64 



11-9 



69 



58 



If we exclude Mauritius, where several anomalous features present 

 themselves, we notice a remarkable uniformity in the values of b/a for 

 declination in Table I. The extraordinarily large differences between 

 the " all " day and " quiet " day (Wild's nwmal day) results at Pawlowsk 

 for vertical force presents itself in every month of the year. Pawlowsk 

 is a station where magnetic disturbances are particularly prominent, 

 and the vertical force there seems particularly sensitive to them. 



§ i. For Greenwich only mean monthly diurnal inequalities were 

 available. Table II gives the mean of the 12 monthly values of 



Table II. 



• 



Place. 



Period. 



Data from — 



Declination. 



Horizontal 

 force. 



1 



a. il0 4 6. 



1 





a. |l0 3 6. 



10 4 b/a. 



Pawlowsk 



1890—1900 



All days 



6-81 



446 



66 



22-8 243 



107 







Quiet days. . 



6-52 



442 



68 



22-2: 208 



94 



Katharinenburg 





All days. . . . 



.... 



6-18 



355 



58 



19-2! 195 



101 



Greenwich. 



1841—1896 



7-29 



377 



52 



26 4| 190 



72 





1865-1896 





7-07 



396 



56 



23 6 215 



91 





1889—1896 



,, .... 



671 



418 



62 



23-7] 218 



92 







Quiet days. . 



6-36 



415 



65 



25-0j 213 



85 





1890—1900 



6*49 



410 



63 



21-5 131 



89 



P 2 



