422 ASTRONOMY. 



steadier light than the rest; and if you continue to 

 observe these for several nights, you will find that 

 they do not appear in the same place among the 

 rest of the stars every night, but that they have 

 motions peculiar to themselves. All the rest of 

 the stars rising and setting always exactly in the 

 same places, are called Jixed stars. Those wan- 

 dering or moving stars are called planets. 



It is now fully proved, that these planets, with 

 the earth which we inhabit, and also the moon, 

 revolve round the sun, which is fixed in the centre 

 of the system. There are two kinds of planets, 

 'primary and secondary. The first move round 

 the sun, and respect him only as the centre of their 

 motions. The secondary planets, called also satel- 

 lites or moons, are smaller planets, revolving round 

 the primary, while they, with the primary planets 

 about which they move, are carried round the sun. 

 The planets move round the sun at various dis- 

 tances, some being much nearer to him than our 

 earth, and others being much farther off. 



There are nine primary planets, which are si- 

 tuated with respect to their distances from the sun 

 as follows: Mercury 5, Venus ?, the Earth ©, 

 Mars s, Ceres, Pallas, Harding, Jupiter n, Sa- 

 turn \, and Herschell or the Georgium Sidus #. 



Of these, our earth is accompanied by one 

 moon ; Jupiter has four moons ; Saturn has seven 

 moons ; and the Georgian planet has six moons. 

 None of these moons, except our own, can be 

 seen without a good telescope. The other five 

 planets do not appear to have any satellites or 

 moons. 



All the planets move round the sun from east 

 to west, and in the same direction do the moons 

 revolve round their primaries, excepting those of 



