150 Mr. Wood HOUSE on the derangements of certain 
After the star had passed the ist and 2d wire, fearing, 
from the appearance of the sky, that clouds might prevent 
me from observing the star on the middle wire, I applied a 
blanket (from want of sufficient preparation only moderately 
warmed) for about 9 minutes, to the upper western brace. 
After the star’s passage over the fifth wire, the blanket, more 
heated than before, was applied to the lower western brace, 
and kept on till the star had passed all the wires. 
Computed passage 
at 3 d wire. 
From passage at ist 27”* U + zi" i5’.6 - - - 48” i6\6 
at 2d 37 43 10 36 .2 - - - 48 19.2 
Mean computed passage - 48 17.9 
Observed ----- 48 12 
Excess - -- -- -- 5,9 
The heating then of the upper western brace caused the 
instrument, or part of it, to deviate to the east, a result which 
agrees with all preceding ones. Next, if we suppose the 
instrument, after the lapse of 20 minutes, to have returned to 
its usual state, and assume 58“ 46% and 9™ 28® to be nearly 
the passages at the 4th and 5th wire, we have 
Computed passages at 
6 th 
7 th 
58” 46’’ + 
f 21”“ 
) 3 i 
. . . 
49 -9 3 
19"’ s 6\7 
3 o"’ 3 S “-9 
9 28 -p 
S 10 
1 21 
32-5 1 . . . 
II .7 3 
20 0.5 
30 39 -7 
Mean computed passages - . - 
Observed - 
19 58 .6 
20 19 
30 37-35 
31 I 
Excesses of observed above computed 
20 ,4 
23.65 
