The Study of Astronomy, adapted to the capacities of youth / In twelve familiar dialogues, between a tutor and his pupil: explaining the general phænomena of the heavenly bodies, the theory of the tides, &c.

by teacher of astronomy John Stedman

Pupil. Ninety-five millions of miles! You astonish me.

Tutor. You will, I dare say, be no less surprized at being told, that he is more than a million of times as large as our earth.

Pupil. It is almost incredible! And what are the planets?

Tutor. The planets are opaque, that is dark bodies, which receive their light from the sun; and, as I told you, revolve about him. The first, or that nearest the sun, is called Mercury, the next Venus, then the Earth, Mars, Jupiter, Saturn, and Georgian, or the Georgium Sidus.[^[3]] These are called primary planets.

Pupil. Are there then any others?

Tutor. Yes. There are fourteen others, which move round their respective primaries as their centers, and with them round the sun, and are called secondaries, satellites or moons.

Pupil. Have all the primaries secondaries?

Tutor. Only four of them have moons. The earth, I need not tell you, has one; Jupiter has four; Saturn seven, besides a stupendous ring which surrounds his body; and Georgian two.

Pupil. In what time, and at what distances, from the sun, do the planets perform their periodical revolutions?

Tutor. Mercury revolves about the sun in 88 days, at the distance of 36 millions of miles.