"Very likely," replied Mary; "and perhaps you would like me to tell you
what those black marks are. They are enormous plains and gloomy caverns
on the moon. A long time ago, perhaps, these plains were bays and seas.
At least, a great astronomer named Galileo thought they were, and he
gave them such pretty names--the Sea of Serenity, the Bay of Dreams,
the Ocean of Storms. But he lived in the days before it was known that
there is not any water on the surface of the moon. Then the caverns on
the moon may once have been volcanoes pouring forth hot lava and ashes,
just as the active volcanoes on the earth. But the volcanoes in the moon
have gone out. They are now like huge dark caverns, some of them more
than fifty miles across. One is three miles deep, and it is named Tycho,
after a great astronomer of olden times.
"Then there are mountains on the moon just like the mountains on earth,
and quite as high. In walking over the moon you would find it very rough
and uneven, but you would not mind this very much, as you would weigh
so much less. Just think, Harry, you would weigh only one-sixth as much
as you do here."
"And what would Uncle Robert weigh?" asked Harry, with a gleam of mischief
in his eye.
[Illustration: PLANET EARTH AND THE MOON.]
"He would only weigh forty pounds," said Mary, laughing; "and if he
played football on the moon, a good kick would send the ball six times
as far away as here. Supposing we were on the moon now, you could throw
a stone at Uncle Robert's house on the other side of the grounds, six
hundred yards away, and hit one of the windows."
"I expect Uncle Robert may be glad then we are not on the moon," said
Harry, laughing; "because I am afraid I should be throwing stones at the
windows all the time. I can see the windows plainly from here. There is
a light in the library."
"Then it must be very late," said Mary, looking over at the house;
"because uncle said he would not be home till nine o'clock. So I can
only tell you one more little story about the moon, and then I must let
you go to sleep. This story is told by the Hindoo people, and gives the
reason why the moon shines with such a soft, silvery light."