ge Capt. Kater’s experiments for determining the 
tance of the centre of oscillation from the axis. This was 
sufficiently guarded against by having the bar so thin as to 
ensure its becoming perpendicular by its own weight, had 
the position of the knife edge been in a small degree erro- 
neous ; for though the form the bar would assume is strictly 
speaking a curve, it may without sensible error be considered 
as a straight line. 
With regard to temperature, every precaution was taken 
to prevent error. The thermometer used was made by Mr. 
Troughton for the late Sir George Shuckburgh. It is divi- 
ded into half degrees, and the height of the mercury may be 
estimated to one tenth of a degree. It has been already ob- 
served in the preceding part of this paper, that the thermo- 
meter was approached only at the first and last coincidences. 
The experiments themselves afford, it is presumed, a suffi- 
cient proof of the stability of the knife edges. Every care 
was taken to form them in the first instance as perfect as 
possible ; and after four sets of experiments had been made, 
they were found on re-measurement to have suffered no per- 
ceptible alteration ; and it is evident by the near agreement 
of the results, that they remained uninjured during the suc- 
ceeding experiments : it is difficult therefore to conceive that 
any error can have arisen from this source. 
I may here remark, that the method I have employed in 
determining the length of the pendulum, possesses other ad- 
vantages besides that of superseding the errors arising from 
unequal density or figure ; and one, not the least considerable 
is, that after a very few vibrations, the true length of the 
pendulum is bounded by certain known limits. Thus in the 
two first sets of experiments, after the re-measurement of the 
