Mr Cajfwi has demonftrated, that in the Polar Star il cauuoi; 
arife from the parallax oi the Magf^us Orbis-^ and our Author 
has given us good arguments to prove the fixt Stars to be at 
To great a diftance, that the Diameter of the Magnus Orhis is 
infenfible in refpeft of it. 
Having thus eftabliftied the Theory of the Primary Pfa- 
nets, in the 4th Book he gives us that of the Secundary, 
whofe motions are much more compofed and intricate than 
any of the firft, theirs being only compounded of an uniform 
progreffive motion forward, and that of Gravity, by which, 
as it virere they are drawn toward the Sun ^ whereas the Se- 
cundaries are not only attrafted towards their refpedive Pri- 
maries 5 but alfo towards the Sun, and that with the fame 
accelerating force of Gravity as the Primaries, when at the 
fame diftance, with a greater force when nearer, and a leller 
when further from the Sun, than the Primaries are. Which 
variety of the force of attraftion, according to the various 
pofitions of the Secundaries Orbit, its inclination to the Orbit 
of its Primary, and the place of the Secundary in tliis Orbit!, 
muft neceffarily produce various inequalities and irregularities 
in the motions of the Secundaries, all which he confiders, 
at large, and from thence he explains the motions of the 
Apfides forwards, that of their Nodes backwards, tiie change- 
able inclination of the Orbits to the plains of their Primaries 
OrbitSjthe different velocities of the Secondaries, according as 
their pofition in refpeft of the Sun, and their Primaries vary 5 
and he apply s the v/hole to the motions of the MoomAll this, 
before the hippy difcoveries of that celebrated Philofopher Mr 
Nemo^^ was not to be attempted by any Phyfical cxpiicati- 
on, the greateft advancement that was made, being only to 
folve them by an Aftronomieal Hy pochefis. He alfo gives us 
an account of j he Tables neceflary to calculate th^ Moons 
place feen out of the £arth, and the manner of ufingthem ^ 
and to this he joyns Mr Nemou's own Theory of the Moon, 
which if ufed in practice, will determine her place nicely 
enough, even in the Qjadracures, as has been found by con- 
garing it withMv Flamji^^d^ obfervatioaSj whm when the 
