6537. PENDULUM, Construction of.—
I have a curiosity to try the length of a pendulum
vibrating seconds here. * * * The bob should
be spherical, of lead, and its radius, I presume,
about one inch. * * * The suspending rod
should be such as not to be affected by heat or
cold, nor yet so heavy as to affect too sensibly
the centre of oscillation. Would not a rod
of wood not larger than a large wire answer
this double view? * * * Iron has been found
but about six times as strong as wood while
its specific gravity is eight times as great. * * *
A rod of white oak not larger than a seine
twine, would probably support a spherical bob
of lead of one inch radius.—
To Dr. Robert Patterson. Washington ed. vi, 26.
(M.
1811)
