§ 2. Most all Stars appear to us, every night in the same position; they seem actually to be _fixed_ in the heavens; and for this reason they are called _fixed Stars_. There are however Ten others, of which it has been ascertained _that they move regularly round the Sun in large circles_. These are called _Planets_ or _wandering Stars_.—The fixed Stars are supposed to be similar to the Sun, in as much as they are bodies which have their own light. The Planets, on the contrary, are of themselves dark bodies, and receive, like our Earth, light and warmth from the Sun. We see them only in consequence of the solar light which they _reflect_ from their surfaces, and this is the reason why they appear to us as bright as the other Stars. § 3. The discoveries of Philosophers have proved beyond a doubt, _that our Earth itself is one of those Planets_, which move round the Sun in stupendous large circles, whose grandeur is hardly conceived by the most powerful imagination. _Our Earth, therefore, is, itself, a Wandering Star_, and the line in which it moves round the Sun is called its _Way_ or _Orbit_. § 4. The Planets, together with our Earth keep each a certain fixed distance from the Sun. On this account they do not disturb each other in their orbits. But they vary from each other in magnitude; although all of them (consequently also our Earth) have a _round_ shape, similar to a ball. In former times men believed that the Earth was flat, or a circular plate on all sides surrounded by water. But this is not true. For it has been proved by a great many observations and actual measurements, that the Earth has a spherical (ball-like) form. Moreover there are navigators who have actually _sailed round the world_, and who have noticed the fact that at sea, the tops of distant objects are seen sooner than the rest; which again proves the spherical form of our Earth. For an illustration you may look at the adjoining plate Plate No. I. The man who is represented as standing on a portion of our Earth, will at first only see the topmast of a vessel at sea; when she comes nearer his eye will discover a much greater portion of her; but when in the third position every part of the vessel will be visible. § 5. Some of the Planets are, in their motion round the Sun, _accompanied by other dark bodies_, which, like the Planets themselves, receive light and heat from the Sun. These are called _Satellites_ or _Moons_. Such a Satellite is the _Moon which accompanies our Earth_; and there are Planets (as we shall see hereafter) which have Four and Six, and One that has even Seven Moons. § 6. Besides the Planets and Moons there is yet another class of bodies, moving round the Sun in exceedingly long ovals. They are but seldom visible, and are distinguished from other heavenly bodies by a tail which is often three, four, and more times larger than the body itself. These are called _Comets_; but their number has not, as yet, been precisely ascertained.