so 
Mr Watts on the Length of the Pendulumy 
To reduce this length to what it would have been had the ob- 
servation been made at the level of the sea, we have the follow- 
ing formula : 
hi 
V I , where V represents the length of the pendulum 
at the level of the sea, I that of the pendulum at the place of 
observation, whose height above the level of the sea is A, and a 
the radius of the earth in the latitude of London : hence we 
shall have 
V 
3013S355 I ax 83x^9^^38355 
5280x3954,583 
inch. 
= S9, 138355 + 0,000311 =39,138666, the length 
of the seconds pendulum in vacuo ^ at the level of the sea, and 
at the temperature of 62° of Fahrenheit’s thermometer, as 
estimated by Sir George Shuckburgh’s standard scale ; or 
inch. 
39,1372405 by General Roy’s scale ; the latitude of the place 
me. 
of observation being 51° 3F 8'',4 North ; or 0,9940999, as es- 
me. 
timated in parts of the metre a bouts;” or 0,99410306, as 
estimated in parts of the metre a traits,” as I have found, by 
Captain Rater’s experiments, that it would be unsafe to wager 
inch, 
that the “ Metre a bouts'^ is less than 39,370949; or that the 
inch. 
“ Metre a traits'^ is greater than 39,370831 of the standard 
scale. 
If we add to 39,138666, the length of the seconds pendulum, 
determined as above, by means of the 5th set of experiments, 
the correction 0,00017 proposed by Mr Trough ton for the spe- 
cific gravities of the brass and the deal ends, we shall have Cap- 
inch. 
tain Rater’s length of the pendulum corrected, 39,138836, 
which differs from the length of the pendulum vibrating seconds, 
as determined by Mr Whitehurst, and corrected by Mr Trough- 
ton, by only 0,000324 parts of an inch in defect. 
It may be also remarked, that if we reject the 1st, 3d, and 
4th sets of experiments, the mean error, or the greatest that is to 
