THE RELATIVE FORCE OF GRAVITY AT KEW AND GREENWICH. 545 
after as it was before each transposition of the pendulum, but its sign would have 
changed, because its direction would have been reversed. The record of the observa¬ 
tions gives no level readings, nor does it give the distances between the tail-piece and 
the arc-scale in the two positions of vibration. All that is known is that the agate 
planes were not maintained in a position of constant horizontality, as in all other 
operations. Thus the results are not strictly differential, and it is to be inferred that 
the large discrepancies occasionally met with between different groups of results, even 
when the individual results in each group are highly accordant, are due to this cause. 
The results of the several operations will now be given. 
Colonel Herschel’s Results, reduced to temperature of 62^ F., and to the 
Density of the Air under the pressure of 26 inches at the temperature 
OF 32° F. 
Determinations at Keiv Observatory. 
Preliminary Vibration-numbers of Pendulum No. 4, before straightening the bar 
and re-grinding the knife-edge. 
Marked face, M, to front. 
Plain face, P, to front. 
Means. 
Set. 
V. 
Set. 
V. 
2 
863 58*74 
15 
86161-44 
3 
86158-84 
16 
86161-02 
4 
86158-05 
17 
86160-87 
5 
6 
8 
86159-21 
86157-31 
86158-41 
18 
19 
20 
86161-25 
86160-60 
86160-24 
Face M . 86158-38 
Face P . 86160-98 
9 
86158-25 
21 
86160-86 
86159-68 
10 
86158-.32 
22 
86161-26 
11 
86158-31 
23 
86160-12 
12 
86158-91 
24 
86160-87 
! 
13 
86158-83 
25 
86161-52 
i 
14 
86157-41 
26 
86161-69 
! 
When this result is reduced to a vacuum, it may be compared with the results 
of the swings by the same pendulum at the same place which were obtained for the 
Indian operations. The reduction to the vacuum may be approximately taken as 
+ 8’32, which gives the vibration-number 86168'00, to compare with 86169'45 
obtained in 1864, before the pendulum was sent out to India, and 86169'57 obtained 
in 1873, after its return from India. 
4 A 
MDCCCXC.—A. 
