[ j<* 3 
given Latitude, derived from the Length of a 
Tendulum that vibrates there in a Second of Time, 
with the centrifugal Force at the Equator, deduced 
from the periodic Time of the diurnal Rotation, and 
the Amplitude of a Degree of the Meridian ; or by 
comparing the Lengths of Tendulums that vibrate in 
equal Times in given unequal Latitudes? or by com- 
paring different Degrees meafured upon the Meridian. 
By the beft Obfervations it would feem, that there is 
a greater Increafe of Gravitation, and of the Degrees 
of the Meridian from the Equator towards the Poles, 
than ought to arife from the Suppofition of an uni- 
form Denfity. Therefore the Author fuppofes the 
Denfity to vary from the Surface towards the Centre ; 
and, in feveral Cafes he has confidered, he finds that a 
greater Denfity towards the Centre would account 
for a greater Increafe of Gravitation towards the 
Poles, but not for a greater Increafe of the Degrees 
of the Meridian ; and that the Hypothefis of a lefs 
Denfity towards the Centre would account for the 
latter, but not for the former, fuppofing (after Sir 
Ifaac Newton) the Columns of the Fluid to extend 
from the Surface to the Centre, and there to fuftain 
each other. On this Account he determines the Gra- 
vitation towards the Earth, when it is fuppofed to be 
hollow with a Nucleus included, according to the 
Hypothefis advanced by Dr .Halley, with the Dif- 
ference of the Semidiameters that might arife from 
fuch a Difpofition of the internal Parrs. But in this 
Cafe, and when the Denfity is fuppofed variable, the 
fpheroidical Figure is only affumed as an Hypothefis. 
He adds, that by imagining the Denfity to be "reater 
in the Axis than in the Plain of the Equator a? equal 
Di- 
