(a88) 
common Center of Gravity, as well that of the Earth, as that 
of the Moon, are to defcribe feveral Epicycles. And, for that 
Reafon fails of giving any clear account of this Menjlrual pe- 
riod. (And in like manner, he propofeth the Conlideration as 
well of the Earths Aphelium and Perihelium , as of the MquinoBi- 
al and Soljlitial Points, in order to the finding a Reafon of the 
Annual VicifEtiides ; but doth not fix upon any thing, in which 
himfelf can Acquiefce ; And therefore leaves it in medio as he 
found it. ) 
It had been more agreeable»to the Laws of Statieks, if he 
had,(" as Ido,) fo confidered the Earth and Moon as two parts 
of the fame movable, ( not fo, as he doth, aliam in Centro et [e< 
quentempracife revolutionem axis , aliam remotius ae velut in cir&am 
ferentia, but, ) fo, as to make neither of them the Center, but 
both out of it, deferibing Epicycles about it: Like as, when 
a long ftick thrown in the Air, whofe one end is heavyer than 
the other., is whirled about, fo as that the End, which did hrft fly 
foremoft , becomes hindmoft > the proper line of motion of 
this whole Body is not that, which is deferibed by either End, 
but that, which is deferibed by a middle point between them ; 
about which point each end, in whirling, deferibes an Epicycle. 
And indeed, in the prefent cafe, it is not the Epicycle deferibed 
by the Moon, bat that, deferibed by the Earth, which gives the 
Menfirual Vfciffitudes of motion to the Water 5 which would, 
as to this, be the fame, if the Earth fo move, whether there were 
any Moon to move or not s nor would the Moons Motion, fup- 
pofing the Earth to hold on its own courfe , any whit concern 
the motion of the Water. 
But •now, Rafter all our Phyficabor Statical Confiderations)the 
eleareft Evidence for this Hypothecs (if it can be had) will be 
from Celeflrial Obfervations. As for inftance j (fee Fip.^P) Sup- 
poling the Sun at S; the Earths place in its Annual Orb at T- and 
Mars (in oppoficion to the Sun, or near itj at M : From whence 
Mars fhould appear in the Zodiack at y> and will at Full moon 
be feen there to be 5 the Moon being at C and the Earth at c: 
(and the like at the New- moon. ) But if the Moon be in the 
Firft quarter at A, and the Earth at a-; Mars will be feen, not at ; 
% but at a ; too flow And when the Moon is at B, and the 
Earth at b? Mars will be feen atJ ; yet too flow : till at the Full- . 
moon* , 
