KAIMirs MACNKTISM 1'KOIHVKH i:Y TIIK MOON AND SUN. 



807 



the more complex one might bo made to fit better than the above figures indicate, if 

 the constants of the formula were altered a little. This, however, is not worth while 

 doing till better observational material is to hand. 



PART III. Tlw Ol>*< r fit tonal Material. 



2G. The following are the data which were available for examining the dependence 

 of tin 1 lunar magnetic variation upon lunar phase : 



Station and period. 



Sub-division of month. 



Seasonal ( li vision. 



Trovandrtim (1854-64) .... 

 Bombay (CHAMBERS) (1846-71) . 



(Moos) (1872-89) . . 

 Batavia (1883-99) 



Bombay (CHAMBERS) (1846-73) . . 



(Moos) (1872-89) . . . 



(1873-79, 1881, 



1883-85) . . . 



Batavia (1883-99) 



DECLINATION. 



Four quarters of month 

 Eight phases 



HORIZONTAL FORCE. 

 Eight phases 



Bombay (Moos) . 

 Batavia (1883-99) 



VERTICAL FORCE. 

 Eight phases 



Separate months of year. 

 Nov.-Jan., Feb.-April, May-July, 

 Aug.-Oct., April-Sept., Oct.-March. 

 Nov.-Jan. 

 April-Sept., Oct.-March. 



As for declination. 

 Nov.-Jan. 



May-July. 



April-Sept., Oct.-March. 



As for declination, 

 it >> 



For purposes of comparison, the Trevandrum results for the separate months of the 

 year have been combined into the four quarters and the two half years (as for 

 Bombay) ; also the 25 hourly values have been reduced to 24. 



The separate tables of the 24 hourly values will not be repeated here, nor the a 

 and b, and C and coefficients of the first four harmonic components which have 

 been calculated from those tables. The harmonic formula used has l>een 



a, cos t + &, sin t + Oy cos 2t + 6 2 sin 2t + a 3 cos 3t + b 3 cos 3< + 4 cos U + 6 4 sin U, 



In the case of all the coefficients a, b, 0, the adopted unit is 10~ 7 G.G.S. units of force 

 (the declination results were also reduced in terms of force), and this was reckoned 

 positive towards the North, West, and upwards (II, D, V). 



$-7. The tables of harmonic coefficients showed that they were subject to an 

 accidental error of amount small in itself, but quite a considerable fraction of the 



2 R 2 



