OF THE EARTH’S MAGNETISM. 561 
Bifilar mean, Singapore Cre 12- phic minus se 21, to oe 1)=— 7:59 
Trevandrum =— 13°30 
Correction to Trevandrum before April 1 (= —4°3 sc. div.) =— 571 
128. 1842, December 18", 19°, and to the end of the month.—Bifilar readings 
affected by spiders; bifilar differences, from December 17 to 31, at Singapore, 
substituted. 
129. 1842, December 30, 31.—Adjustment and new magnet, No. 5, employed 
Bifilar mean, Singapore (1843, Dat 8-13), minus (1842, Dec. 11-16) = + 3-57 
: Trevandrum = + 46°44 
aa 
Trevandrum bifilar correction during 1842 : 5 = + 41°87 
130. 1843, April 25.—The bifilar magnet was ohne to the sun while the 
observatory was being re-thatched; this produced a loss of magnetism, and 
rendered another adjustment necessary. The means April 25 to May 5 were 
supplied from Singapore, the difference from the means of preceding eight days 
being taken. After which the scale readings, corrected to 70° Fahr., were 
diminished by 100 and multiplied by 1:06, to reduce tothe same value of &. The 
following comparison was made :— 
By Singapore bifilar means ee U3 cari ), minus (April 21, 23, os = — 12°85 
By Trevandrum, : =—13:17 
The difference being so in no correction has been Aperue 
131. 1843, June 20, 21; July 17-23.—-Affected by spiders, and the means in- 
terpolated with reference to other places. 
132. 1843, July 24 to 30.—Evidently affected by a constant strain of spider 
thread ; in consequence, from comparison with Singapore, July 24-28, are cor- 
rected by—2°8 and July 30 (in the middle of which day the threads were removed) 
by —1°4. 
133. 1843, December 15-31.—Some accidental cause produced a change, 
December 15. 
By Singapore Centar oe 17-22), minus Shepeicin 3-8) = 42:24 
By Trevandrum, ee 7 
Correction applied to Trevandrum after December 15, - =+4-21 
134, 1844, March 31.—Adjustment,— 
By Singapore (April 1-3) minus (March 25-27) . . = —838 
This difference applied to the mean at Trevandrum for April 1-3, showed that 
the means before the adjustment should have 43:1 (=30°8 sc. div.) added, to 
connect the series. The means at Makerstoun, taken 14 days before and 14 days 
after adjustment, gave the correction 30:9 sc. div., almost exactly the same. The 
daily means before March 31 were reduced to those after by the formula,— 
(N—178'2) 0:98 + 209-0 se. div., 
where N is the daily mean before March 31. 
135. The following daily means are supplied from Singapore, on account of 
