64: SABINE’S EXPERIMENTS. 
vibrations which a single pendulum continued through the whole interval of 
the experiments at each station would have made, the force of gravity at 
London and at New-York, will appear to be in the inverse proportion of 
seal; © searaal a whence, if the length of the seconds pendulum in London 
be 39, 1393 inches of Sir George Shuckburgh’s Standard Scale, its length at 
New-York will be 39, 1012 inches of the same scale; this determination be- 
ing subject to a correction, amounting possibly to a single unit in-the last 
figure, when the expansion of the pendulums of comparison due to differ- 
ences of temperature, shall have been correctly ascertained gi further expe- 
riment. 
it may not be uuinteresting to annex to the preceding details, an account 
of the going of two other pendulums of comparison at New-York dnd at Lon- 
don, also invariable except by changes of temperature, but differing from the 
former in the mode adopted in experimenting with them, being applied suc- 
cessively to a clock which preserved their motion by its maintaining power, 
and registered their oscillations: the clock and pendulums were the same 
which I had employed in determining the acceleration between London and 
Melville Island, as recorded in the philosophical transactions for 1821; since 
which time, however, the clock had been cleaned and the knife edges of the 
pendulums ground afresh. The clock was set up at New-York in the Antiroom 
to the Library of the College, which is immediately beneath the apartment in 
which the detached pendulums were used ; its going in the same interval from 
the 22d of December to the 4th of January, was ascertained by comparison 
with the chronometer No. 423, whose rate has been already shown: during 
this period no fire was lighted in the stove ; but, as it would have been inconve- ~ 
nient to have darkened the apartment, the changes of temperature in the 24 
hours were greater than in the room above, and though still not very consider- 
able, would have required a far more frequent registry than it would have been 
