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 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 figure.
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.