transit instruments by the effect of temperature. 151 
The effect, therefore, of the expansion of the lower western 
brace was a retardation of the star, in its upper culmination, 
to the amount of about 20 s , a result which accords both with 
the explanation given of the cause of the instrument's devia- 
tion, and with former results. 
The above experiments were not conducted, as I have 
already said, with much attention to nicety, which would 
have been an useless quality, seeing that the object of the 
experiments was not to enable me to modify the position or 
size of the braces, but to justify the measure of entirely 
discarding them as fallacious auxiliaries of the instrument. 
With the view, however, of communicating equal accessions 
of heat rather more accurately than by the preceding imper- 
fect mode of applying a heated blanket, I held, in some of the 
following experiments, for the same time, and nearly about 
the same parts, the braces of the instrument, one in each 
hand. 
October 24th. Upper culmination. 
2 
3 
4 
5 
6 
7 
Polaris. 
m. s. 
37 37 
m. s. 
48 19 
m. s, 
58 48 
m. s. 
9 2 9 
III , S. 
20 5 
ID. S, 
30 56 
After the star had passed the middle wire, I held, for about 
9 minutes, the two western braces, one in each hand. 
