( ) 
fervations in Jupiter , there is no doubt but it will 
be more exadt in the Earth, vvhofe Diameters are 
much nearer to Equality. 
7. By Experiments made at Jamaica * in the 
Latitude of 18 Degrees with a very curious Clock, 
contriv’d by Mi*. Graham , it was found that the 
London Pendulum went flower there by 2' 6" in a 
Sydereal Day, than at London . But it was found 
by Experiments made with Thermometers, that 9" 
were to be allowed for the lengthening of the Pen- 
dulum by Heat 5 and therefore it was retarded 
only i* 57" by the Decrement of Gravity. So 
that while a Pendulum of London makes 86164 Vi- 
brations, the Number of Seconds in a Sydereal 
Day, the fame at Jamaica only gives 86047 Vibra- 
tions. Therefore the Force of Gravity at London 
is to that in the Latitude of 18 Degrees, as the 
Square of 86164 to the Square of 86047 ; that is, 
very nearly as 1106 to 1103. And (by Article 1, 
and 2.) if a denote the mean Diameter of the 
Earth, d the Difference of the greateft and fmalleft; 
c c Cl 
a — —will denote the Force of Gravity in general 
in any Latitude, whofe Co-fine is to the Radius 
as c to r : Where, if in the Place of c there be 
fubftituted the Co-fines of 5 1 0 : 32' and 18 9 : o', 
that is of the Latitudes of London and Jamaica , 
we fhall have the Force of Gravity at the former 
to that at the latter, as a — [3870 d to a — (9045' d , 
that is as 1106 to 1103. Whence the mean Di- 
ameter of the Earth will be to the Difference of the 
Axis 
* See Tranfatt. N°*43i. p. 301. 
o 
