will allow them liberty enough to place the
Celestial Bodies at what distance they please.

If therefore we would come to any certainty in this point, we must go other
wayes to work; and as I have here examined the height and refractive
property of the Air by other wayes then are usual, so must we find the
Parallax of the Planets by wayes not yet practiced; and to this end, I
cannot imagine any better way, then the Observations of them by two persons
at very far distant parts of the Earth, that lye as neer as may be under
the same Meridian, or Degree of longitude, but differing as much in
latitude, as there can be places conveniently found: These two persons, at
certain appointed times, should (as near as could be) both at the same
time, observe the way of the _Moon_, _Mars_, _Venus_, _Jupiter_, and
_Saturn_, amongst the fixt Stars, with a good large _Telescope_, and making
little Iconismes, or pictures, of the small fixed Stars, that appear to
each of them to lye in or near the way of the Center of the Planet, and the
exact measure of the apparent Diameter; from the comparing of such
Observations together, we might certainly know the true distance, or
Parallax, of the Planet. And having any one true Parallax of these Planets,
we might very easily have the other by their apparent Diameters, which the
_Telescope_ likewise affords us very accurately. And thence their motions
might be much better known, and their Theories more exactly regulated. And
for this purpose I know not any one place more convenient for such an
Observation to be made in, then in the Island of St. _Helena_, upon the
Coast of _Africk_, which lyes about sixteen degrees to the Southwards of
the Line, and is very near, according to the latest Geographical Maps, in
the same Meridian with _London_; for though they may not perhaps lye
exactly in the same, yet their Observations, being ordered according to
what I shall anon shew, it will not be difficult to find the true distance
of the Planet. But were they both under the same Meridian, it would be much
better.

And because Observations may be much easier, and more accurately made with
good _Telescopes_, then with any other Instruments, it will not, I suppose,
seem impertinent to explain a little what wayes I judge most fit and
convenient for that particular. Such therefore as shall be the Observators
for this purpose, should be furnished with the best _Telescopes_ that can
be had, the longer the better an