472 CAPTAIN SABINE ON THE LENGTH OF THE SECONDS PENDULUM 
§ 2. Weight below. 
Abstract of three series of experiments from which the reduction to a vacuum 
is derived for the vibrations of the pendulum with the weight below. 
Reference 
to the 
details. 
Temp. 
Vibrations. 
Reduction 
to mean 
temp. 57°. 
Vibrations at 57°. 
Barom. or Gauge. 
inch. 
'I A 
56.95 
86057.30 
— 0.02 
86057.281 
r 29.7271 
In free air .... 
c B 
57-60 
86056.88 
+ 0.26 
86057.14 >86057-25 
«( 29.756 V 29.740 
J D 
5670 
86057.48 
-0.13 
86057.35J 
I29.737J 
Air withdrawn . 
c 
56.95 
86068.28 
—0.02 
86068.24 
1.950 
(Slider at 1 .5) 
Differences 
10.99 
27.790 
In free air .... 
N 
57*50 
86056.84 
+ 0.22 
86057-06 
29.457 
Air withdrawn . 
H to M 
56.87 
86068.67 
— 0.06 
86068.61 
1.211 
(Slider at 1.633) 
Differences 
11.55 
28.246 
In free air .... 
Air withdrawn . 
/FF 
1 GG 
VV to EE 
57-50 
58.00 
56.75 
86056.88 
86056.53 
86068.71 
+ 0.22 
+ 0.44 
-0.11 
86057-10 ) oCnrfT 
86056.97/ 860 j7 * 01, 
86068.60 
{tw } 39 - 349 
0.976 
(Slider at 1.566) Differences 
11.56 
28.373 
From these three series we have the following differences ; viz. 
10.99 vibr. corresponding to 27-790 in. of air at 57-1 ; or 11.86 vibr. to 30 in. 
11.55 28.246 at 57.5 ; or 12.26 
11.56 28.373 at 577 ; or 12.22 
Whence we obtain the reduction when the weight is below, in the proportion 
of 12.10 vibrations per diem for 30 inches of air at 57°.4. 
The mean pressure within the glasses during the fourteen experiments with 
the weight below, (from which, as will be seen hereafter, the rate of the pendu- 
lum was finally derived,) was 1.07 inch: the reduction for which, according to the 
proportion found above, is 0.43 of a vibration per diem. This amount would be 
altered only one hundredth of a vibration, were the partial result most distant 
from the mean substituted for the mean of the three results by which the 
reduction was determined. 
