m the Length of the Pendulum vibrating Seconds, 321 
ter was carefully noted ; the weight of the wire by which the 
pendulum was suspended, was 56 grains, and the weight of water 
equal in bulk to that part of the wire which was immersed was 
2,5 grains. The temperatuure of the water was 68®, and that 
of the atmosphere 62® ; the barometer 29,9 inches. Hence we 
have the weight of the pendulum 66858,8 grains in vacuo, at 
the temperature of 62® ; the weight of an equal bulk of water 
at the same temperature, 9068,4 grains ; and the resulting spe- 
cific gravity of the pendulum, 7,3727. 
Employing this specific gravity in computing the allowance 
for the mean buoyancy of the atmosphere, we obtain ,00624 for 
this correction instead of ,00545, the former erroneous conclu- 
sion. Besides this, the allowance -J- ,00031 for the height of 
the pendulum above the level of the sea, should, according to 
Dr Young’s investigation, have been multiplied by making 
H- ,00021 of an inch. These corrections being applied, we 
have 39,13929 inches of Sir G. Shuckburgh’s standard scale, 
for the length of the pendulum vibrating seconds in the latitude 
of London. 
Wishing to compare with this, the result which would have 
been obtained by means of the weights and specific gravities of 
the different parts of the pendulum, I carefully measured the 
deal ends, and found them to contain 3,956 cubic inches. The 
weight of the knife edges was 370 grains, and their specific gra^ 
vity 7,84. 
With these data, and taking the specific gravity of deal at 
0 , 49 ; the specific gravity of the whole pendulum will be found 
to vary from the more accurate determination above given, a 
quantity which would have occasioned a difference in the length 
of the seconds pendulum of only of an inch. 
Place of Observa- 
vation. 
Latitude. 
Vibrations in 
a mean solar 
day. ' 
Length of the Pendulum 
vibrating seconds in 
parts of Sir George 
Shuckburgh’s scale. 
Unst, 
Portsoy, 
60!45l28'01 
86096,90 
Inches. 
39,17146 
57.40.58,65 
86086,05 
39,16159 
Leith Fort, 
55.58.40,80 
86079,40 
39,15554 
Clifton, - - 
53.27.43,12 
86068,90 
39,14600 
Arbury Hill, - 
52.12.55,32 
86065,05 
39,14250 
London, 
51.31. 8,40 
86061,52 
39,13929 
Shanklin Farm, 
50.37.23,94 
86058,07 
39,13614 
