as in the former Article, becaufe the periodick Time 
of Jupiter round the Sun is vaftly greater than 
that of his third Satellite round him. 1 have chofe 
the third Satellite before any of the reft, becaufe its 
greateft Elongation was obferv’d by Dr. Tound y 
with a Micrometer adapted to aTelefcope 123 Feet 
long ; and he alfo took the Diameter of Jupiter 
by the Tranfit of the Satellite, which is a much 
more exa<ft Way than with a Micrometer. But as 
the Planes of Jupiter' s Satellites almoft coincide 
with the Plane of his Equator, the Diameter, de- 
termined by the Tranfit of the Satellite, is his 
greateft 5 and the Diftance of the Satellite, which 
ought to have been given in his mean Diameters, is 
afligned in his greateft : For which Reafbn the Force 
of Gravity already found, muft be augmented in the 
triplicate Ratio of his greateft Diameter to his mean 
one ; that is, if a reprefent the mean Diameter, and 
d the Difference of the longed and fhorteft, in the 
Proportion oixa-\-idtoza very nearly. Hence, 
as the centrifugal Force at his Equator, to the mean 
Force of Gravity on his Surface, fo is Unity to 
11 And(byArticle 4 .) 1 1 ix — ± 1 1 r 
:: a : or 20 aa = 18 6 ad 2. 79 dd ; which 
makes a to d y as 108 to 10 ; and thence the Axis is 
to the equatoreal Diameter, as 108 — 5 to 108 + 5, 
or as 103 to 11 3 3 that is, as 12 to 13 L 6 : Which 
agrees nicely with the Obfervations of both Dr. 
Pound and Mr. Bradley , made with Huygens's Long 
Telefcope ; the former making it as 12 to 13, and 
the latter as 2y to 27, which is very nearly the 
fame. And if this Theory agrees fo well with Ob- 
fervations 
