in the length of the pendulum vibrating seconds. 415 
most obligingly complied, and favoured me with his assistance, 
and with every requisite for making the experiment. 
A deal trough was prepared seven feet long, nine inches 
wide, and the same depth. The pendulum was slung hori- 
zontally from the scale pan, by a fine iron wire. The weight 
of the whole was carefully determined in air, and found to be 
66904 grains. The trough which had been previously placed 
beneath the pendulum, was then filled with distilled water, 
and the weight of water displaced was found to be 9066 
grains. The small portion of iron wire which was immersed 
in the water 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 temperature 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 specific gravity of the pendulum, 7,3727. 
Employing this specific gravity in computing the allowance for 
the mean buoyancy of the atmosphere , we obtain ,00624 f or 
correction instead of ,00545, the former erroneous conclusion. 
Besides this, the allowance ,0003 1 for the height of the pen- 
dulum above the level of the sea, should, according to Dr. Young's 
investigation, have been multiplied by making -(- ,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 
