Academia scientiarum, or, The academy of sciences being a short and easie introduction to the knowledge of the liberal arts and sciences, with the names of those famous authors that have written on every particular science : in English and Latine / by D. Abercromby ...

Sect▪ IV. Astronomy.

AStronomy gives us an account of the Motions of Coelestial Bodies, of of their distance, order, bulk, &c. The Ba∣bylonians will have Belus to have been the Inventor of it, the Aegyptians Mercury, the Moors Atlas and Hercu∣les, the Grecians Jupiter, Orpheus and Atreus, the Scythes Prometheus. We may divide it into two Parts, the one Spherical, and the other we may call Systematical The Spherical is that part of Astronomy which treateth of the Sphere, whether Artificial or Natural; the Artificial Sphere is made up of ten circles, whereof six are great ones, because they divide the whole Sphere into two equal parts, such we reckon the Horizon, the Meridian, the Equator, the two Colures, and the Zodiack. The little Circles are those that divide the Sphere

into two unequal parts, as the two Tro∣picks, and the two Polar Circles: Every circle is divided into sixty parts, which they call first minutes; and each Minute likewise into sixty parts, which we call second Minutes.

The Natural Sphere, or the Coelestial Globe, besides the foregoing Circles, of∣fers to our view divers Constellations: The Antients reckon'd eight and forty, comprehending in this number all the Stars to be seen in Greece, and all the known Parts of the World; 12 of those Constellations are contain'd in the Zo∣diack, 21 are to be seen toward the North, and 15 towards the South; but of late there are twelve other Constellations discovered towards the South.

The Systematical Astronomy, which others call the Theorical, is that part which by the help of some Engines and Orbs, offers to our view those Coelestial Motions which are not so obvious to every common understanding.

This part of. Astronomy comprehends several Hypotheses, as that of Anaxa∣goras and Democritus, who allowed a free motion to the Stars, but of no first Mover, or Primum mobile: Neither did they admit any second motion to∣wards ihe East, but a simple motion only towards the West; so in their Opinion, those Stars only could be said to move toward the East, that moved more slowly towards the West. There is another Hypothesis that considers the Stars as tied to solid Spheres; and who hold this Hypothesis, hold likewise the Earth to rest in the Centre of the World.

Copernicus allows motion to the Earth; he fixeth the Sun in the Centre of the World, though it turns round about its own Axis within seven and twenty days, as 'tis manifest by the mo∣tion of its spots. 1. In this System, the Orb of the sixed Stars is immoveable. 2. Mercury turns round the Sun in almost three months. 3. Venus in four months

and a half, and the Earth itself in twelve months, and round the Earth the Moon tarneth every month. 4. Mars's revolu∣tion round the Sun is ended in almost two years, as Jupiter's in twelve years, and Saturn's in thirty.

Tycobrahe orders his System thus: First the Firmament, or the Sphere of the fixed Stars, the Earth being the Centre of the World; then the Orbs of Saturn, Jupiter and Mars; Venus and Mercury turn round the Sun, and the Moon round the Earth.

The Old System was ordered thus: The Earth was the Centre of the World, a∣bove it were plac'd the Planets and Hea∣vens in this order; the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, the two Chrystalline Heavens, and the Primum mobile.

Authors.

Ptolomy, Aratus, Eudoxus, Calippe, Tycobrahe, Gassendy, de Billy, Cour∣cier, de Sacrobosco, Fracastorius, Ga∣lilaeus.