239 
made with an invariable pendulum. 
interval between the observation. For the stars we have 171, 
and for the sun 110 ; so that the final number of vibrations 
may be taken as 86095,54. 
The ball of the pendulum was twelve feet above the level 
of low water, the correction for which, by the duplicate ratio 
t 
of the distances from the earth’s centre, is nearly o v ,o5 in 
twenty-four hours. As the station was the tabular surface 
of an old stream of lava, not very compact, I suppose the 
proper multiplier is T 6 ^, which will give o v ,o 3 for the correc- 
tion due to this elevation. 
The mean height of the barometer was 29,93, and the 
mean temperature 8o°,9, whence it appears that the specific 
gravity of the pendulum was to that of air, as 7458 to 1, 
which gives 5 V ,77 as a correction to be added to the number 
of vibrations to arrive at the number it would have made in 
vacuo ; and adding also 0,03 for the elevation, we have 
86101 ,34 for the number of vibrations made by the pendulum, 
at the level of the sea in vacuo at 68° of Fahrenheit, in a 
mean solar day, at the Galapagos, in latitude o° 32' 19" north, 
and longitude 90°^- west. 
The same pendulum in London made 86235,98 vibrations 
in the same interval, and reduced to the level of the sea. 
Whence the length of the seconds pendulum at the Gala- 
pagos, deduced from the duplicate ratio of these vibrations, 
and assuming the length of the seconds pendulum in London 
39,13929, appears to be 39,0171692, or 39,01717 inches of 
Sir G. Shuckburgh’s scale. 
By comparing the lengths of the seconds pendulum at the 
principal stations in the British survey as ascertained by Cap- 
tain Kater’s experiments, the diminution of gravity from the 
pole to the equator, and the resulting ellipticity, are as follows : 
