length of the pendulum vibrating seconds . 6 1 
scopes having been examined to see that the lines bisected 
the angles formed by the spider’s threads, the trough was 
filled with hot water to the edge of the bar, and two thermo- 
meters were placed in it, one just beneath the surface of the 
water, and the other at the bottom of the trough. The bar 
rapidly expanded, and the line on it was followed by the 
micrometer till it became stationary. The bisection was then 
perfected, and the mean of the degrees shewn by the ther- 
mometers registered, together with the number of revolu- 
tions and parts made by the micrometer. The whole was 
now suffered to remain till the temperature had become 
several degrees lower, when the contraction of the bar, occa- 
sioned by such decrease of temperature was measured, and 
thus several successive observations were made, which are 
contained in the following table. 
Distance between the lines on the bar, 49,5 inches. 
Highest 
Lowest 
Diff of 
Divis. of the 
Expansion in parts of the 
Temp. 
Temp. 
Temp. 
micrometer. 
length for each degree. 
9° 6 
43 
O 
53 
620 
,000010116 
93 
43 
50 
580 
,000010030 
Distance between the lines on the bar, 50,5 inches. 
9i 
43 
48 
600 
,0000106l6 
89 
84 
5 
70 
,000011890 
83 
75 
8 
89 
,000009448 
75 
61 
1 4 
149 
,000009038 
80 
44 
36 
400 
,000009436 
80 
60 
20 
21 5 
,000009129 
73 
60 
13 
152 
,000009930 
Mean of the whole. 
,000009959 
