_Of the Motions of the Planets in general_ 183 _Of the Stations and Retrogadations of the Planets_ 186 _Of the Annual and Diurnal Motion of the Earth_ 194 _Of the Phases of the Moon, and of her Motion in her Orbit_ 201 _Of the Eclipses of the Sun and Moon_ 208 _Of the Eclipses of_ Jupiter’_s Satellites_ 212
A Brief Account of the SOLAR SYSTEM, and of the FIXED STARS.
_Of the Order and Periods of the Primary Planets revolving about the Sun; and of the Secondary Planets round their respective Primaries._
The Sun is placed in the midst of an immense space, wherein six opaque spherical bodies revolve about him as their center. These wandering globes are called the _Planets_, who, at different distances, and in different periods, perform their revolutions from West to East, in the following order:
1. ☿ _Mercury_ is nearest to the Sun of all the planets, and performs its course in about three months. 2. ♀ _Venus_ in about seven months and a half. 3. ♁ The _Earth_ in a year. 4. ♂ _Mars_ in about two years. 5. ♃ _Jupiter_ in twelve. And lastly, ♄ _Saturn_, whose[1]_Orbit_ includes all the rest, spends almost 30 years in one revolution round the Sun. The distances of the Planets from the Sun are nearly in the same proportion as they are represented in _Plate_ 1. _viz._ Supposing the distance of the Earth from the Sun to be divided into 10 equal parts; that of _Mercury_ will be about 4 of these parts; of _Venus_ 7; of _Mars_ 15; of _Jupiter_ 52; and that of _Saturn_ 95.
The Characters placed before the names of the Planets, are for brevity’s sake commonly made use of by Astronomers, instead of the words at length, as ♀, for _Venus_, &c.
THE SOLAR SYSTEM Or the Orbits of the Planets _according to their mean distances from the Sun_.]
The orbits of the Planets are not all in the same plane, but variously inclined to one another; so that supposing one of them to coincide with the above scheme, the others will have one half above, and the other half below it; intersecting one another in a line passing through the Sun. The plane of the Earth’s orbit is called the _Ecliptic_; and this the astronomers make the standard to which the planes of the other orbits are judged to incline. The right line passing thro’ the Sun, and the common intersection of the plane of the orbit of any planet and the Ecliptic, is called the _Line of the Nodes_ of that planet; and the points themselves, wherein the orbit cuts the Ecliptic are called the _Nodes_.