402
and future, especially if the time be for many Moneths or Years; I
am therefore forced, with other Observations, and more exact than
the former, and in times more remote from one another, to correct
the Tables of such Motions, and limit them even to the shortest mo
ment: for such exactnesse my first Observations suffice not; not only
in regard of the short intervals of Time, but because I had not as then
found out a way to measure the distances between the said Planets
by any Instrument: I Observed such Intervals with simple relation
to the Diameter of the Body of Jupiter; taken, as we have said, by
the eye, the which, though they admit not errors of above a Minute,
yet they suffice not for the determination of the exact greatness of the
Spheres of those Stars. But now that I have hit upon a way of ta
king such measures without failing, scarce in a very few Seconds, I will
continue the observation to the very occultation of JVPITER,
which shall serve to bring us to the perfect knowledge of the Moti
ons, and Magnitudes of the Orbes of the said Planets, together

also with some other consequences thence arising. I adde to these
things the observation of some obscure Spots, which are discover
ed in the Solar Body, which changing, position in that, propounds
to our consideration a great argument either that the Sun revolves in
it selfe, or that perhaps other Starts, in like manner as Venus and
Mercury, revolve about it, invisible in other times, by reason of their
small digressions, lesse than that of Mercury, and only visible when
they interpose between the Sun and our eye, or else hint the truth
of both this and that; the certainty of which things ought not to be
contemned, nor omitted.

The Authors
Observations of
the Solar Spots.

Continuall observation hath at last assured me that these Spots are
matters contiguous to the Body of the Sun, there continually produced
in great number, and afterwards dissolved, some in a shorter, some in a
longer time, and to be by the Conversion or Revolution of the Sun in it
selfe, which in a Lunar Moneth, or thereabouts, finisheth its Period,
caried about in a Circle, an accident great of it selfe, and greater for
its Consequences.

The occasion in
ducing the Au
thor to write
this Treatise.

As to the other particular in the next place. ^{*} Many causes have
moved me to write the present Tract, the subject whereof, is the
Dispute which I held some dayes since, with some learned men of
this City, about which, as your Highnesse knows, have followed
many Discourses: The principall of which Causes hath been the
Intimation of your Highnesse, having commended to me Writing,
as a singular means to make true known from false, reall from appa
rent Reasons, farr better than by Disputing vocally, where the
one or the other, or very often both the Disputants, through too