fidereditin relation to the Sun, in refpedfc whereof, its motion is 
regular, he confiders the fame in relation to the Earth , where We 
obferve it > and thews by the means of his Th£fer,what is to be ad- 
ded or fubftra&ed, to know, at what time the faid Spot is to come 
into the middle of Jupiter's Diske , according as he is Oriental or 
Occidental. He hath alfo confidered it in relation to an un mova- 
ble point, which he has fuppofed to be the firlt point of Aries, be- 
caufe we thither refer here upon Earth the beginning of all the 
Celeftia! motions, and there is the Primum mobile , that one would 
imagine, if we were in Jupiter , as we do here imagine Ours of 24. 
hours. 
The Difcovery is one of the beft, that have been yet made in 
the Heavens ; and thofe,that hold the Motion of the earth, find in 
it a full Analogy. For , Jupiter turning about the Sun, does never- 
thelefs turnabout his Axis 5 and although he be much bi gg er 
than the Earth, he does neverthelefs turn much more fwiftly than 
it, fince he makes more than two Turns, and a third part, for its 
one j and carries with him 4. Moons,as the Earth does one. 
This Obfervation ought to excite all Curious per foils to endea- 
vour the perfecting of Optic \ Glajfes ,to the end that it may be'difeo- 
vered 5 whether the other Planets Mars, Venus and Mercury, about ^ 
whom no Moon hath as yet been difeovered , do yet turn about 
their Axes, and in how much time they do fo 5 efpeeially Mars, in 
whomfome Spot is difeover'd, and Venus ? wherein M Burattim 
hath fignified from Poland^ he has obferv’d Inequalities, as in the 
Moon. 
It will be worth while, to watch for the feeing of Jupiter again 
this Spring, that this happy Obfervation may be confirmed in db 
vers places, and endeavours ufed to make new ones. 
» 
A11 Account of feme Books, lately publijhed. 
I. Hydrojlatical Paradoxes ymade out by Nen> Experiments {for the 
moflpart Pbyjical, and Eafie ) by the Honourable Egbert Boyle. This 
Treatife,promifed in Numb.%, of thefe Papers, is now come forth: 
And was occafioned by the perufal of the Learned Monfieur Paf 
challs Tracft, Of the /. Equilibrium of Liquors , and of the Weight of the 
Air : Of which two Subjects, flatter having been more clearly 
made out in England by Experiments,, which could not be made by 
Monfieur Pafchal and others , that Wanted the advantage of fueh 
Engines and fnftruments, as have here been frequently made life 
A a a off 3 
