cause of all her Motions. And
though, even now also, we may, by such Observations in one station, as here
at _London_, observe the _apparent Diameter_ and motion of the Moon in her
_Dragon_, and consequently be inabled to make a better ghess at the
_Species_ or kind of Curve, in which she is mov'd, that is, whether it be
sphaerical, or _elliptical_, or neither, and with what proportional
velocities she is carried in that Curve; yet till her true _Parallax_ be
known, we cannot determine either.

Next, for the true distance of the Sun, the best way will be, by accurate
Observations, made in both these forementioned stations, of some convenient
Eclipse of the Sun, many of which may so happen, as to be seen by both; for
the _Penumbra_ of the Moon may, if she be sixty Semidiameters distant from
the Earth, and the Sun above seven thousand, extend to about seventy
degrees on the Earth, and consequently be seen by Observators as far
distant as _London_, and St. _Helena_, which are not full sixty nine
degrees distant. And this would much more accurately, then any way that has
been yet used, determine the Parallax, and distance, of the Sun; for as for
the Horizontal Parallax I have already shewn it sufficiently uncertain; nor
is the way of finding it by the Eclipse of the Moon any other then
hypothetical; and that by the difference of the true and apparent
quadrature of the Moon is not less uncertain, witness their Deductions from
it, who have made use of it; for _Vendeline_ puts that difference to be but
4'.30". whence he deduces a vast distance of the Sun, as I have before
shewn. _Ricciolo_ makes it full 30'.00. but _Reinoldus_, and _Kircher_, no
less then three degrees. And no wonder, for if we examine the _Theory_, we
shall find it so complicated with uncertainties.

First, From the irregular surface of the Moon, and from several Parallaxes,
that unless the _Dichotomy_ happen in the _Nonagesimus_ of the _Ecliptick_,
and that in the Meridian, &c. all which happen so very seldom, that it is
almost impossible to make them otherwise then uncertainly. Besides, we are
not yet certain, but that there may be somewhat about the Moon _analogus_
to the Air about the Earth, which may cause a refraction of the light of
the Sun, and consequently make a great difference in the apparent
_dichotomy_ of the Moon. Their way indeed is very rational and ingenious;
and such as is much to be preferred before the way by the Horizontal
Parallax, cou