62 Lieutenant Foster's account of 
The sums of the factors, however, being 275,5 in this 
series, and only 66 in the second, we obtain for the final 
number of vibrations at Port Bowen, 
By the method of disappearance - - 86230,172 
By the mean of disappearance and re-app. 86230,313. 
From the above data and number of vibrations made by 
the same pendulum from the mean of both series at Green- 
wich, viz. 
by the method of disappearance - - 86159,368 
and by mean of disappearance and re-app. 86159,500, 
together with the assumed length of the seconds' pendulum 
at Greenwich 39, 1391 1 inches ; the length of the seconds' 
pendulum at Port Bowen is found to be nearly 39,203464 
inches, by the method of disappearance, and by the mean 
of disappearance and re-appearance 39,203472 inches ; and 
comparing these with 39,*39H inches, the assumed length 
in lat. 51 0 28' 39" N. as before stated, the diminution of 
gravity from the pole to the equator will be by the method 
of disappearance ,0054152, the ellipticity of the earth , 
and the length of the equatorial pendulum 39,009805 inches ; 
and by the mean of disappearance and re-appearance, the 
diminution of gravity from the pole to the equator will be 
,0054159, the ellipticity of the earth 5^77, and the length 
of the equatorial pendulum 39,009789 inches of Sir George 
Schuckburgh’s scale. 
The length of the pendulum vibrating seconds, not having 
been determined at Greenwich, but at Mr. Browne's house 
in London, it must be remembered that the above lengths 
are not the true lengths of the pendulum, but are merely 
given for the sake of comparison. 
