EARTH AND SUN. 283
LL. Yes.

P. One of them was, that a man standing with one
leg upon the saddle and riding full speed, threw up
balls into the air and catched them as they fell.

L£. L remember it very well.

P. Perhaps you would have expected these balls to
bave fallen behind him, as he was going at such a rate.

L. So I did.

P. But you saw that they fell into his hand as
directly as if he had been standing quite still. That
was because at the instant he threw them up, they re-
ceived the motion of the horse straight forward, as well
as the upright motion that he gave them, so that they
made a slanting line through the air, and came down
in the same place they would have reached if he had
held them in his hand all the while.

L. That is very curious, indeed!

P. In the same manner, you may have observed, in
riding in a carriage, that if you throw anything out of
the window, it falls directly opposite, just as though
the carriage were standing still, and is not left behind

ou.
J LL I will try that, the next time I ride in one.

P. You are then to imagine the sun to be a mighty
mass of matter, many thousand times larger than our
earth, placed in the centre, quiet and unmoved. You
are to conceive our earth, as soon as created, launched
with vast force in a stra‘ght lme, as though it were a
bowl on a green. It would have flown off in this line
for ever, through the boundless regions of space, had
it not, at the same instant, received a pull from the sun,
by its attraction. By the wonderful skill of the Creator,
these two forces were made exactly to counterbalance
each other ; so that just as much as the earth, from the
original motion given it, tends to fly forwards, just so
much the sun draws it to the centre; and the conse-
quence is, that it takes a course between the two, which
ig a circle round and round the sun.

£. But if the earth were set a-rolling, like a bowi