His
telescope was indeed too small to show any features of interest in
Mars, though the planet of war is much nearer to us than Jupiter. Mars
is but a small world. The diameter of the planet is about 4,400 miles,
that of our earth being nearly 8,000. Jupiter, though much farther
away, has an immense diameter of more than 80,000 miles to make
up, and much more than make up, for the effect of distance. With his
noble system of moons he appears a remarkable object even with a
small telescope, while Mars shows no feature of interest even with
telescopes of considerable size.
It was not, then, till very powerful telescopes had been constructed
that astronomers learned what we now know about Mars.[4]
[Footnote 4: See the "Moons of Mars" in "Letter Box" Department]
It is found that his surface is divided into land and water, like the
surface of our own earth. But his seas and oceans are not nearly so
large compared with his continents and lands. You know that on our own
earth the water covers so much larger a surface than the land that
the great continents are in reality islands.
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