in the length of the pendulum vibrating seconds. 343 
from that described in the Philosophical Transactions before 
referred to It was contrived in such a manner as to be 
attached to the iron frame by three screws, and was levelled 
by placing thin sheets of lead between it and the frame, a 
method which was preferred from its promising a great degree 
of firmness. 
An arc divided into degrees and tenths for ascertaining the 
extent of the vibrations of the pendulum, was attached to a 
piece of wood which fitted into the opening of the door of the 
clock case. 
Expansion of the pendulum. 
When the bar of the pendulum was prepared, previous to 
the weight being soldered to it, its expansion was determined 
in the same manner as is described in the Philosophical 
Transactions before referred to. The results were as follow : 
Distance between the lines on the Bar 39,54 
inches. 
Highest 
Temp. 
Lowest 
Temp. 
Diff. of 
Temp. 
Div. of 
Microm. 
Expansion in parts 
of the length for 
each degree. 
0 
125,0 
125,0 
99,0 
73 > 8 
O 
56,3 
99.0 
73 > 8 
63.0 
68 ,7 
26,0 
25,2 
10,5 
648 
245 
220 
91 
,00001022 
,00001021 
,0000094.6 
,00000938 
Mean 
,00000982 
Hence the expansion of the pendulum appears to be 
,00000382 parts of its length for each degree of the thermo- 
meter; and the corresponding correction to be applied to the 
number of vibrations in 24 hours for such change of tempera- 
ture will be 0,423. 
