458 
MR. BAILY ON THE CORRECTION OF 
however, have been revised, especially those which exhibited any remarkable 
anomaly: and I trust that no error of importance will be found to exist. 
During the progress of the experiments, the apparatus has been from time to 
time altered, in order to suit the circumstances of the case : and trifling differ- 
ences of specific gravity, and of comparative lengths and weights arising there- 
from, may consequently have passed unnoticed and unobserved. Indeed the 
subject has been altogether so new, that in commencing a set of experiments, 
I was not always aware of the precise points, to which it was most necessary 
to direct the attention ; and which were not sufficiently apparent till after the 
result was obtained. Should it however be desirable to repeat any of these 
experiments, in a manner that may be considered likely to lead to more accu- 
rate results, I shall be happy to resume the enquiry. 
The Chevalier Du Buat’s Experiments. 
During the course of these enquiries, it will be seen that I have, all along, 
considered M. Bessel as the first discoverer of that peculiar property of the 
moving pendulum, which it has been the object of this paper to elucidate : and 
undoubtedly, he is entitled to the merit of having first applied those principles, 
which he has investigated with so much accuracy and with such great ability, 
to the modern pendulum ; and thus rendered it a more powerful and delicate 
instrument in the hands of the practical and theoretical philosopher. But, it 
has recently been found that this same property of the pendulum was known 
nearly fifty years ago, and distinctly treated by the Chevalier Du Buat in his 
Principes d’Hydraulique. In that work, the second edition of which appeared 
in 1 78G *, the author has stated the results of a number of experiments on pen- 
dulums of various kinds, swung in air and in water ; from which he was led 
to infer that a quantity of the fluid in which the pendulum oscillates, is dragged 
with it in its motion, and thus retards its vibrations. He remarks that “ if a 
“ denotes the length of a pendulum making any number of vibrations in vacuo, 
“ / the length of a pendulum making the same number of vibrations in the 
“ fluid, p the weight of the moving body in the fluid, P the weight of the fluid 
* The first edition (1779) does not contain the experiments here alluded to. 
