meafurmg Heights with the Barometer. 767 
as I know, who hath taken the denfity of the medium 
in which it performed its vibrations into the account, and 
given us its length at the equator in vacuo. But if w© 
are to judge of the denfity of the air in the frigid zone 
from the barometrical obfervations at Spitzbergen, the 
pendulum there muft have loft fo much of its weight, as 
to have leffened confiderably the number of vibrations 
below what they would have been in vacuo, in the fame 
temperature. Having confidered the effect that this 
would produce, I collected the bell experiments that 
have hitherto been made with the pendulum into one 
view, and having applied the equation that the denfity 
of the air, in which they feverally vibrated, feemed ta 
require; I found from computation, that the ratio of the 
diameters of the earth is (as Mr. bouguer fuppofed it) 
nearly that of 178 to 179, inftead of 229 to 230, as 
edimatedby Sir Isaac newton, and which agrees very 
nearly with the mean refult from the meafurement of 
the degrees of the meridian. The experiments with the 
pendulum are fo fimple and eafy, may be repeated fo 
often in all fituations, and are fo much more confident 
with each other, than the meafured lengths of degrees 
of latitude, that it appears to be incomparably the bed 
method for determining the figure of the earth. And it 
it fhould really be found fo flat a fpheroid as the pendu- 
Vol. LXVII. SF him 
