OF THE VIBRATIONS OF AN INVARIABLE PENDULUM. 
235 
Whence the vibrations within the receivers are in this experiment in defect, 
0.21 per diem. 
Collecting the three results in one view, they are as follows : 
Feb. 1 7. Exp. IX. The vibrations within the glasses in excess 0.34 
Feb. 21. Exp. X. The vibrations within the glasses in defect 0.15 
Feb. 22. Exp. XI. The vibrations within the glasses in defect 0.21 
Mean. The vibrations within the glasses in defect 0.007 per diem. 
We may therefore conclude that the vibration in air within the glasses, and 
in the free air of the apartment, the glasses being removed, will lead by suffi- 
cient repetition to an identical result. 
Finally, the knife edge being examined, was found apparently as clean and 
sharp as when first used. The agate planes had retained their horizontality ; 
and the screws securing the planes to the circular plate, and the plate to the 
iron frame, were as tight as when the experiments were commenced. 
We have now to collect in one view the several results, from whence the re- 
duction to a vacuum for an invariable pendulum vibrating in air is to be de- 
rived. 
Exp. I. June 1828. 
II. July 1828. 
III. Jan. 1829. 
IV. Jan. 1829. 
V. Jan. 1829. 
VI. Jan. 1829. 
VII. Feb. 1829. 
VIII. Feb. 1829. 
London . . 
London . . 
Greenwich 
Greenwich 
Greenwich 
Greenwich 
Greenwich 
Greenwich 
. . . . 7-38 " 
i 
r d 
£J 
' 22.765 " 
O 
O* 
. . . . 9.065 
O 
Ph 
27.721 
CO 
. . . . 9.54 
in 
27.459 
-t-J 
. . . . 9.17 
. . . . 10.38 
is ; coi 
ing to 
26.138 
29.109 
S.s J 
>• 1=2 < 
P O 
. . . . 5.705 
.2 
16.080 
O 
. . . . 10.525 
c3 
U 
30.193 
CO 
. . . . 10.560 
> 
.30.113 
, 
0 
c L 
72.01 
69.70 
35.89 
32.37 
36.40 
35.65 
38.10 
41.25 
Mean 9.042 
26.197 
45. 1! 
2 h 2 
