L 55 3, 
direct ratio of their maffes (i to 39.788) the fum 
will be the ratio of their denfities, that of 1.19143 
to 1, a little lefs than 6 to 5. 
3. Suppofing ftill the fame femidiameter of the 
orbit as before, the force of gravity will be to the 
Earth’s attractive force on the Moon as 3670.94 to j , 
and to the Moon’s force on the Earth as 40.788 times 
that number, or 149730.4, to 1. 
Again, the force ot the Moon upon that furface 
of the ocean to which tine is vertical, being to her 
force on the Earth’s centre, as the fquare of 60.5883 
to that of 59-5883 ; and the difference of thele 
fquares being to the latter as 1 to 29.54623, this 
difference of the forces will fupport the weight of 
one 4423968th part of the water at the vertex. 
And, becaul'e the Earth’s femidiameter is fmall in 
companion to the Moon’s diftance, the like differences 
of force will decreafe from the furface to the centre, 
nearly in an arithmetical progreffion, as the weight 
of the water does ; making the cafe analogous to the 
diminution of gravity by centrifugal force. 
But it is likewife eafily fhewn, that half this quan- 
tity of lunar force exerts itfelf to deprefs the waters 
all around at the didance of 90 degrees from the 
vertex ; i. therefore of the former fraction, that is one 
-2949312 part of the force of gravity, will be the to- 
tal caufe of the difference in heigth of the flood and 
ebb, in an open and boundlefs ocean. 
Say therefore, if (in determining the figure of 
the earth) of gravity, fufpended by the centri- 
fugal force, gave, for the difference of diameters T ^. T , 
what will one 2949312 part give ? and tjae anfwer, 
in feet, will be 8.887; 
