24 
HAROLD’S DISCUSSIONS. 
about the sun in a path nearly thirty times as far 
from tlie sun as the earth is, and its year is more than 
one hundred and sixty-four times as long as the 
earth’s. 
The earth and all the planets outside its orbit have 
moons or satellites revolving about them as they them- 
Fig. 9.—A spiral nebula in the constellation of the Great Bear. 
A mass of light, as it appears in the telescope. 
selves revolve about the sun. The earth has one moon, 
Mars two, Jupiter, the largest planet of all, has five 
moons, and Saturn has eight moons and two w^onder- 
ful rings. Uranus and IN^eptune are so far away that 
it is difficult, even with good telescopes, to see their 
satellites, but thus far it is agreed that Uranus has 
