45} the second
Face of _Mars_, he could not see it the 14. and 16. of _April_.

From all which Observations he Judges it to be evident, that the Period of
this Planets Revolution is not perform'd in the space of 12. hours 20,
minutes, but in about 24 hours 40 minutes; more exactly to be determin'd by
comparing distant Observations: And that those who affirm the former, must
have been deceived by not well distinguishing the two Faces, but that
having seen the second, taken it for the first.

All which he concludes with this Advertisement, that, when he defines the
time of the Revolution of _Mars_, he does not speak of its _Mean_
Revolution, but onely of that, which he observ'd, whilst _Mars_ was
opposite to the Sun; which is the shortest of all.

_The Figures of the _Principal_ Observations, represented in the Book
here discoursed of, may be seen in the annexed _Scheme_; _videl.__

K. _One of the Faces of _Mars_, as S. _Cassini_ observed it _March 3.
(_st.n._) 1666_ in the Evening, with a Glass of 24 Palmes._

L. _The other Face, as he saw it _Febr. 14/24_ in the Evening._

M. _The first Face, as S. _Campani_ saw at Rome, _March 3. 1666_. in the
Evening, with a Glass of 50 Palmes._

N. _The second Face, as the same _Campani_ observed it _March 18/28_. in
the Evening._

O. _The figure of _Mars_ as it was seen at _Rome_ by a Telescope of
_Divini_ of 45 Palmes, _March 20/30_._

P. _The Figure of the said Planet, as it was seen the same day and hour at
Bononia by _Cassini_; being that of the second Face._

* * * * *

_Some Observations lately made at _London_ concerning the Planet
_Jupiter_._

These, as they were made, so they were imparted, by Mr. _Hook_, as follows:

[Illustration]

A. 1666, _June_ 26. between 3. and 4. of the Clock in the morning, I
observed the Body of _Jupiter_ through a 60 foot-glass, and found the
apparent Diameter of it through the Tube, to be somewhat more than 2.
degrees, that is, about four {246} times as big, as the Diameter of the
_Moon_ appears to the _naked_ Eye. I saw the Limb pretty round, and very
well defin'd without radiation. The parts of the _Phasis_ of it had various
degrees of Light. About a and f, the _North_ and _South_ poles of it (in
the _Fig Q._) 'twas somewhat darker, and by degrees it grew brighter
towards b. and e, two Belts or Zones; the one of which (b) was a small dark
_Belt_ crossing the Body Southward; Adjoyning to wh