OF THE EARTH’S MAGNETISM. 563 
139. 1842, May 13.—It appears to me that some accidental cause of change 
was acting at Singapore from this date till May 25. The preceding table of daily 
changes of force from the 13th May at Hobarton, Trevandrum, St Helena, will 
show the grounds on which this belief is founded. The Singapore daily means 
after May 13, being corrected by the means of the changes at Hobarton, Trevan- 
drum, and St Helena, and the differences (corrected means minus observed means) 
taken, the last column was obtained. The daily means, May 14-25, corrected 
from the observations at the three places, have been substituted; and as the last 
days, May 26-30, show a mean permanent diminution of 1:2 sc. div. (=1°68), 
this quantity has been added to the observations before May 14th. 
140. 1842, July 24.—An accidental change appears to occur,— 
By Trevandrum bifilar means (J a 25- ea minus SH ns 18— ape =+ 1:86 
St Helena : =+ 1:93 
Hobarton a he of oot =+ 1:37 
Mean , ane yet eee =+ 1°72 
Singapore aie ser See mie = +19-26 
Therefore, correct Singapore before July 24, by . : . +1754 
July 24 is supplied from the three places—changes from the 22d being, 
Trevandrum. St Helena. ) Hobarton. Mean. 
July 24, minus 22, — 2:55 — 3°32 — 2-56 — 2°81 
141. 1843, February 25.—An accidental change appears to occur, 
By Trevandrum bifilar means (Feb. Pio to March ue, minus vay: uate = + 3°82 
Hobarton =+3-99 
St Helena ae oie ee = +2°58 
Cape of Good Hope .. see era eas = +543 
Mean ame jen one ete =+38'95 
Singapore Hee ae cae 208 = + 8:53 
Correct Singapore before February 25, by . 5 ° : +4-58 
142. 1844, April 28.—Accidental change at Singapore, — 
By Trevandrum bifilar means (ape: 28— ai) minus mths ez 24) =— 570 
Singapore = —11°75 
Correct Singapore before April 28, by. : 3 —6:05 
143. 1845, January 21—-22.—An accidental tates occurs between 21st and 
22d: 
By Trevandrum bifilar means (Jan, a minus (Jan, 13-17) = — 4:06 
Singapore Be =+3-19 
Correct Singapore before January 21, by : : : , +725 
The correction of + 7:0 was applied. 
144. The accidental changes at Singapore, it appears to me, may have been 
due to some slight variation in the position of the telescope; as the accidental 
VOL. XXII. PART III. 7F 
