416 
THE ASTRONOMER ROYAL ON THE DIURNAL AND ANNUAL 
from which the annual change was found to be 0’0063, or in parts of the whole 
horizontal force +0-0017. 
Applying the proportional parts of this annual change for the several months with 
the sign changed, the following numbers (all requiring the addition of 0-8830 nearly) 
are obtained as expressing the monthly values of northerly horizontal force 
January . . . 
. 0-1172 
February . . . 
. 0-1175 
March .... 
. 0-1185 
April .... 
. 0-1196 
May .... 
. 0-1195 
June .... 
. 0-1189 
July 
. 0-1172 
August . . . . 
. 0-1171 
September . . , 
. 0-1172 
October . 
. 0-1167 
November . . . 
. 0-1167 
December . . . 
. 0-1167 
From these are obtained the following Excesses of Corrected Horizontal Force for each 
month above the mean of all the months : — 
Annual Inequality of Northern Horizontal Force. 
January 
-0-0005 
February . . . 
-0-0002 
March .... 
+ 0-0008 
April .... 
+0-0019 
May 
+0-0018 
June .... 
+ 0-0012 
July .... 
-0-0005 
August .... 
-0-0006 
September . . 
-0-0005 
October . . . 
-0-0010 
November. 
-0-0010 
December . . . 
-0-0010 
On comparing these two series of monthly numbers, for Declination and Horizontal 
Force, with those in the two periods treated in the preceding paper, it does not appear, 
I think, that there is such agreement as justifies us in concluding that there is any real 
yearly inequality distinct from the secular inequality. There will, however, always be 
some doubt on conclusions applying to horizontal force in different months, on account 
of the uncertainty of correction for temperature ; but no such doubt attaches to the 
declination. 
