273 
made with an invariable pendulum. 
We have thus obtained 86125,56 vibrations by the stars, and 86125,73 by the 
sun ; the sums of the factors being respectively 78 and 132, we may take S6125,66 
as the final mean number of vibrations made by the pendulum in 24 hours. 
The height of the pendulum above the level of low water was found by levelling 
72 feet ; the correction due to winch is ,293 j and as the ground beneath and im- 
mediately round the pendulum was granite, and sloping rapidly to the sea, it maybe 
go 
multiplied by , which gives ,18 as the correction for the elevation. 
103 
The correction for buoyancy is 5,86, which added to ,1S, gives 6,04 as the ulti- 
mate correction to be added to S6125,66 ; and thus we obtain 86131,70 for the 
number of vibrations this pendulum would have made in vacuo at the level of the 
sea, in temp, of 68° of Fahrenheit in a mean solar day at Rio de Janeiro in lati- 
tude 22° 55' 22", longitude 43° W. 
From the foregoing data, and the number of vibrations made at the level of the 
sea inLondon by the same pendulum, on the return to England,* viz. 86236,95, and 
39,13929 inches the length of the second’s pendulum in London, we arrive at the 
length of the second’s pendulum at Rio de Janeiro 39,043S1 inches, whence the fol- 
lowing results are deduced. 
Stations compared with Rio de 
Janeiro, in Latitude 22° 55 / 22" S. 
Diminution of Gra- 
vity from the Pole to 
the Equator. 
Ellipticity. 
Length of 
Equat. l’end. 
O / // 
1 
Unst 
in Lat. 60 45 28 N. 
,0053671 
304,55 
39,01204 
Portsoy . . 
. . . 57 40 59 
,0053672 
1 
304,57 
,01204 
Leith Fort . 
. . 55 58 41 
,0053508 
l 
,01214 
303,03 
Clifton . 
. . 53 27 43 
,0053042 
1 
,01242 
298,84 
Arbury Hill 
. . 52 12 55 
,0053495 
1 
302,94 
,01215 
London . 
. . 51 31 8 
,0053079 
1 
,01240 
299,16 
Shanklin Farm . . 50 37 24 
,0053087 
1 
,01239 
299,24 
Mean 
,0053365 
1 
301,77 
39,01223 
1 
* See Remarks after the Experiment, in the Appendix. 
mdcccxxiii. N n 
