460 
MR. BAILY ON THE CORRECTION OF 
were made. And although he remarks that the above mean value of n is given 
as generally suitable to all cases of spheres, yet he suspects that the quantity 
of dragged fluid is rather less with large spheres than with small ones, and also 
that it is rather less for short pendulums than for long ones *. 
But, is it not a remarkable circumstance in the history of this subject, that 
these important and apparently conclusive experiments of M. Du Buat, which 
were made by the order and at the expense of the French Government, which 
were examined, at the request of the Minister of War, by the Royal Academy of 
Sciences at Paris, and by them favourably reported on, which were first published 
in the year 1/86 (little more than 10 years prior to the experiments of M. Borda 
on the length of the pendulum |), and which excited so much interest that they 
led to the subject for the Prize Essay, proposed by the Academy in the follow¬ 
ing year; and which, not being answered, was repeated in the year 1791, with 
the offer of a double reward;—experiments which attracted at that time so 
much public attention that another edition of the work appeared in 1816, just 
about the time when the subject of the pendulum was revived in the different 
states of Europe ; which has not only been translated into the German lan¬ 
guage £, and praised in the highest terms by some of their principal writers on 
that subject, but has been also largely quoted in many English works, and freely 
commented on in this country :—is it not singular that such experiments should 
have been so soon and so completely lost sight of, and forgotten, that not one 
of the many distinguished individuals actually engaged in those pursuits, and 
in the investigation of this subject, should have had the least idea or remem¬ 
brance of the additional correction for the reduction to a vacuum so clearly 
pointed out by M. Du Buat : and that until the re-discovery of this principle 
by M. Bessel, as detailed in his valuable paper on the pendulum, no one should 
* The first suspicion is verified by the present experiments; at least, in the light in which M. Du 
Buat viewed the subject. For though the quantity of dragged fluid is greater with large spheres than 
with small ones, yet the factor n, which he appears to have considered its index, is less. The second 
suspicion is also confirmed not only by some of the present experiments, but likewise by those of 
M. Bessel, alluded to in the note in page 434. 
j I am unable to fix the precise date of M. Borda’s experiments : for, although the month and the 
day, as well as the exact time to the nearest second, are minutely recorded, I have not been able to 
detect the year in which they were made. 
X By J. F. Lempe, Leipsic 1796. See also the works of Langsdoke, and others. 
