THE PLANETS, 
169 
5. The planets are twenty-nine in number. They are divided into 
two classes, The first class embraces what are called primary 
planets, because they revolve immediately around the sun. 
6. The other class comprises the secondary planets, Mmoons, or 
satellites. They revolve immediately around their respective prima- 
ries, and go around the sun in Company with those bodies. 
7. The satellites are much smaller than the planets around which 
they move. They give light to those bodies in the same manner that 
the moon enlightens the parts of the earth that are turned from the 
sun. The satellites present the same changes, or phases, that we 
see in the moon, 
8. The primary planets are eleven in number, "Their names are, 
Mercury, Venus, the Earth, Mars, Vesta, Juno, Ceres, Pallas, Jupi- 
ter, Saturn, and Uranus. 
9. The secondary planets, or Mo0ns, are eighteen in number. Of 
these the earth has one moon, J upiter four, Saturn seven, and Ura- 
NUs six. 
10. Five of the primary planets, viz. Mercury, Venus, Mars, Jupi- 
ter, and Saturn, were known to the ancients before the birth of our 
Saviour. The other five have been discovered by modern astrono- 
mers, within the last fifty or sixty years, 
11. The planets perform their revolutions around the sun in differ.- 
ent periods of time, and at different distances. Those planets near 
the sun, perform their revolutions in less time than those that are 
farther off, because they move faster, and have less distance to g0. 
LESSON 81. 
THE PLANETS. 
1. Mercury is the planet nearest to the sun. It is the most rapid 
in its motion of any of the planets, and is much smaller than the earth, 
many planets are there ? — What is the first class called? 6. What does the other 
class comprise? 7. What are the satellites— How do they give light? — What 
do the satellites present? 8, How many primary planets are {here ? — Which are 
they? 9. How many secondary planets are there? 10. Which five of the pri- 
mary planets were known to the ancients before the birtlı of our Saviour? 11, How 
do the planets perform their revolutions round the sun ? — Why do the planets near 
the sun perform their revolutions in Jess time than those that are farther off? 
Questions, — 1, What is Mercury ? — What is said of tlıe motion, Se. ol