[ 2 5 ] 
(properly corrected) will, by the reafoning in th e 
abovementioned letter, give the diftance of a moon, 
circulating round an unmoveable earth, equal to 
59.95792 femidiameters of the equator. For the 
logarithm of this number, which is 1.7778438, 
write /. 
Let L be the logarithm of fome greater mean 
dift ance, inferred from obfervations of the moon’s 
parallax ; and if r be the natural number to the 
logarithm 3 X L — /, and M be taken equal to 
“p, the mafs of the earth will be to that of the 
moon, as M to r. 
Converfely, If M be any how determined, 
its equal and r, with its logarithm 3 X L — / 
are known ; 4 of which is L — / to be added to /. 
For inftance, if, with Sir Ifaac Newton, we put 
39.788, the diftance will be 60.4557, 
logarithm L being 1.7814372. 
II. If, for each of thefe three, the moon’s mafs, 
her accelerative force on the earth, and her diftance 
from the earth’s centre, we write ( <p = ) 1 : the 
accelerative force of the earth on the moon will be 
reprefen ted by M, the mafs juft now computed. 
And if F is the fun’s accelerative force on the earth, 
x* his diftance in femidiameters of the lunar orbit, 
Qjhe ratio of a fidereal year to a periodic month j 
F M 
we have (by Cor. 2. Prop. 4. Princip. I.) - -^r ; 
a given ratio in given terms. 
Vol.- LV 1 II. 
E 
III. The 
