(28l) 
For which, this conGderation of the Common Center of Gravity 
of the Earth and Moon , is fo proper a remedy C efpecially if it 
fliall be found precifely to anfwer thofe Fhcenomena , which I 
have not Examined, but am very apt to believej that it is fo 
far from being, with me, an Objed:ion againft it, that it is one 
of the reafonSjWhich make me inclinable to introduce it. 
1 muft before 1 leave this , add one ConGderation more. 
That if we fliall upon thefe ConGderations think it reafonable, 
thus to conGder the Common Center of Gravity of the Earth and 
AdQoniiim^y as well be thought reafonable^ that the like Con- 
Gderation Ihould be had of Jupiter and his four Satellites jVih\c\\ 
according to the Complication of their feveral motions j will 
fomewhat change the poGtion of Jupiter^z% to that Common cen-- 
ter of Gravity oi all thefe Bodies ; which yet, becaufc of their 
fmallnefs, may chance to befo little, as that, at this diftance, 
the change of this apparent place may not be difcernable. And 
what is faid of Jupiter , is in the like manner to be underftood 
of Saturne and his Satelles , difcovcred hj Hugenius: For all 
thefe Satellites are to their Principals^ as fo many Moons to the 
Earth. And I do very well remember, in the Letters forecited, 
yiv^Horrocks expreffeth fome fuch little inequalities mSaturnes 
motion, of which he could not imagine what account to give, 
as if (toufe his ExprejSion) this crabbed Old Saturn had defpi- 
i^Ah'is Youth. Which, for ought I know , might well enough 
have been accounted for , if at that time ih^Satellesoi Saturn 
had been difcovered, and that MnHbrw;^/ had thought of fuch 
a motion as the Common Center of Gravity of Saturn and his Compaq* 
nion.to be conGderab!e,as to the guiding of his motion. 
You have now 5 in obedience to your Commands 5 an Ac- 
count of my thoughts, as to this matter, though yet immature 
and unpoliflied : What ufe you will pleafe to make of them , I 
(hall leave to your prudence^&c. 
APPENDIX, written by Tpay of Letter to the Publilher ; 
Being an Anfwer to fome ObjgUions^ made by feveral Ferfins^ to 
t^e precedent Di[courfe\ 
1 Received yours > and am very well contented, that objeBi" 
onshc made againft my Hypothefis concerning Tydes : being 
Pp 2 pro- 
