260 
Captain Hall's details of experiments 
By the transits of the stars we have obtained 86120,24 vibrations made by the 
pendulum, and by the sun 86120,04 ; but the sums of the factors for the stars being 
27, and those for the sun 20, we have 0,15 to add to the vibrations given by the sun 
to arrive at 86120,19, the mean number of vibrations in 24 hours. 
The ball of the pendulum was elevated above the level of the sea 115 feet, the 
correction due to which is 0,47 X = 0,28 j this, together with 5,71 , the correc- 
tion for buoyancy of the atmosphere, gives 5,99 as the final sum to be added to the 
mean number of vibrations in 24 hours, which gives 86126,18 for the number of 
vibrations made by the pendulum in vacuo at the level of the sea, and temperature 
68° at San Bias de California, in latitude 21° 32' 24" N, longitude 105° 15' West. 
From the above data, and the length of the second’s pendulum in London, deter- 
mined after the return,* the length of the second’s pendulum at San Bias appears 
to be 39,038S1 inches, and comparing this with the lengths ascertained at different 
places, by Captain Kater, we obtain the following results : — 
Stations compared with San Bias, 
in Lat. 21° 32' 24" N. 
Diminution cf Gra- 
vity from Pole to 
Equator. 
Ellipticity. 
Length of the 
Equat. Pend. 
Unst - in Lat. 60 45 28 N. 
,0054273 
1 
39,01026 
310,25 
1 
Portsoy - - - 57 40 59 
,0054323 
,01024 
310,73 
Leith Fort - - 55 58 41 
,0054193 
1 
,01031 
309,48 
Clifton - - - 52 27 43 
,0053799 
1 
,01052 
305,75 
Arbury Hill - - 52 12 55 
,0054268 
1 
,01027 
310,21 
London - - - -51 31 8 
,0053888 
1 
,01047 
306,59 
Shaklin Farm - 50 37 24 
,0053923 
1 
,01045 
306,92 
Mean 
,0054095 
l 
308,56 
39,01036 
* See Remarks after the Experiment given in the Appendix. 
