t 40 ] 
down to Mr. Jefferson, late secretary of state, who 
has treated the subject in question, in a report to 
congress, all agree in opinion, “ that matter by its 
mere extension furnishes nothing invariable,’’ and 
that recourse must therefore be had to its motion. 
That a pendulum vibrating seconds of time, in any 
place, in any given latitude, will be of the same 
length, in the same latitude, in any other place, 
however remote the two places may be from each 
other, provided it vibrates in places on the level of 
the ocean ; and that “ such a pendulum, becomes 
itself a measure of determinate length, to which all 
others may be referred, as to a standard,” 
But as the center of oscillation, in a pendulum 
with a bob, is not susceptible of accurate determin-f 
ation, several writers on this subject have proposed 
as a substitute for such a pendulum, a rod without 
a bob, particularly the ingenious Mr. Graham, who 
in 1721, so constructed a rod, that neither the ex¬ 
tension of the metal, of which it was constructed, 
occasioned by heat, or its contraction from cold, 
liad any perceptable effect on its length, and he 
found that it vibrated seconds for a very long time 
without any sensible error. 
Having premised thus much, the following 
deductions will be made from an uniform cy-. 
lindrical rod, that shall vibrate seconds of time, 
on the level of the ocean, and in the comple¬ 
tion of the forty.fifth degree of latitude ; for 
