cftimates to be, 9 hours and 5 6 minu tC5. 
For 2LS Kepler did before con jcfture, from the motion of 
tha Primitive Planets about the Sua as their Center^ that the 
San moved about its own Axis, but could not prove it, till 
by Galiho and shmer th,Q Spots in the Sua were difcovered h 
fo it hath been thought reafonable, from the Secundary Pla- 
nets moving about Jitprter, that J ftp iter is jsilfo moved about 
his Axis ; yet, till now, it hath not been evinced by Obfer- 
vation, That it doth fo moves muchkfs, in what Period of 
Time. And the like reafon there is to judge fo of Saturn^ be- 
caufeof the Secundary Planet difcovered by Monfieur H«- 
gens de Zulichem to move about it 5 (though fuch motion be 
not yet evinced from Obfervation ;) as well as that of the 
£^r^^, from its Attendant the 
Whether the fame may be alfo concluded of the other 
Vhntts^ Marf^Vemf^QLtid Jlfercurjf^ Cabout whom have not 
yet been obferved any Secondary Planets to move, ) is not 
fo evident, Yetthcrp may be fomc^rhat of like probability 
in ihofe. Not oael^, becaufe it is poflible they may have 
Secundary Planets about them, though not yet difcovered ^ 
(Fora we know, it was long after thofe otjuptter^behxe that 
about Saturn was difcovered 5 and who knows, what after 
times may difcover about the reft 0 But becaufe the Primary 
Planets being all in like manner inlightoed by the Sun , and 
(inatllikely hoodj moved by it; it is likely that they be 
moved by the fame Laws aud Methods^ and therefore,tujn'd 
about their own Axis, as it is manifcft that fome of them 
are. 
.But, as for the Secundary Planets, as well thofc about 
Jupiter^ as that about Saturn 5 it is moft likely that they have 
no fuch Rotation upon their Axis. Not fo much, becaufe^ 
by reafon of their fmalncfs, no fueh thing hath been yet ob- 
fcrved, or^ indeed, could bej though it were true 5) Bm be- 
caufe tlxey being Analogical to OMvMoon^ it ii moft likely 
that they are moved in like manner. Now, though it be 
true. 
