nr 
Or 
x 
OF THE EARTH'S MAGNETISM. 
Bifilar mean (April 14, 15, 16, 17), minus bifilar mean (April 8, 9, 10, 11). 
Cape of Good Hope, = —8:23 
Trevandrum, == 2 @)oy71 
Singapore, — —7:18 
Hobarton, = — 6°83 
Mean of four places, = —7:87 
Makerstoun, — — 568 
The means at Makerstoun after April 13 should therefore be corrected by + 2:2. 
This correction has not been applied. 
113. 1845, December 3.—Arms of torsion circle turned and returned. 
Bifilar mean (November 28, 30, December 1, 2) minus (December 4, 5, 7, 8). 
Trevandrum, . i u = — 6:02 
Singapore, . : : ; 5 = —4:96 
Hobarton, = 232 
Mean of three, t ; 3 = — 4:43 
Makerstoun, . : : é ‘ = —E0)7/ 
The means of Makerstoun after December 3 should therefore be corrected by 
—(°36. The correction has not been applied.* 
114. 1846, January 1.—Arms of torsion circle moved forward. In this case 
the amount of scale reading changed was found to agree with the change of 
torsion circle reading. To verify the change we have the following com- 
parison :— 
Bifilar mean (December 28, 29, 30, 31) minus (January 2, 4, 5, 6). 
Makerstoun, : ‘ , : = +3:29 
Hobarton, . ’ : ‘ i =+329 
The exact agreement is of course accidental. 
115. Care or Goop Hopz,+ 1843, April—Adjustment. No observations of 
the bifilar at the Cape have been published for the month of April 1843; it has 
been difficult, therefore, to connect the series before and after the adjustment of 
that month. Had the monthly means before and after the adjustment agreed 
with those at St Helena for the corresponding months, St Helena observations 
might have been employed as guides. This, however, is not the case, the 
monthly changes after May being very different at the two places. The only 
other monthly means available for such a correction are those at Singapore and 
Trevandrum, where the secular variation for the same epoch resembles some- 
what that at the Cape. 
* The Cape means not employed, as the readings were descending rapidly by secular or instru- 
mental change at the time. 
+ Lat, 33° 56’ S., Long. 1" 13™ 56s E. of Greenwich. Observations, vol. i, printed under the 
superintendence of Lieutenant-Colonel E. Sasinz. 
