transit instruments by the effect of temperature. 149 
. 
Computed transits at 
sth 
6th 
7 th 
C 42“22«.5 
From transit at ist 26“ 5 8'+<52 55 V 
20*. 5 
53 " 
32" 
(63 34 j 
(31 43*0 
at 2d 37 39 + ^42 15.6% 
22 .1 
54-6 
33 'S 
(52 5+.8) 
(21 6.91 
at 3d 48 18 + -{ 31 39.4 V 
24 -9 
57 -4 
36.6 
(^42 18.6) 
Mean computed passages 
9’”22 •li'lg"' 
3 o” 34 -J 3 
Observed . . _ 
9 3 ‘ 
20 3 
30 47 
Excesses of observed above computed - - 
8.S 
8 
12 .87 
. 
These excesses indicate a deviation of the instrument to 
the 'west; but their quantities show that the deviation arose 
from \he difference of the effects produced by the expansions, 
since it is only one third of the deviation produced by applying 
the blanket diagonally to the braces. 
It is not at all essential to the explanation I have given of 
the cause of the instrument’s deviation, that the braces on the 
same side, even if equally heated, should exactly counter¬ 
act each other. The effect of counteraction, under such cir¬ 
cumstances would, probably, vary with the individual instru¬ 
ment. It might be greater in one than in another of similar 
construction ; but, in the above experiment, it is not at all 
likely that the braces were equally heated, since, probably, 
they were not enveloped either with equal portions of the 
blanket, or portions equally heated. 
Oct. 23. Upper culmination. 
I 
2 
3 
4 
5 
6 
7 
m. s. 
27 I 
s 
m. s. 
48 12 
m. a. 
58 46 
m. s. 
9 28 
m. s, 
20 19 
s. 
3 * I 
Polaris. 
