, or the Dog-star.
All these, he continually observed, journeyed every night from east to
west, and then appeared the evening after in their former places. "How
strange it is," observed Tommy, one day to Mr Barlow, "that all these
stars should be continually turning about the earth!"

"How do you know," replied Mr Barlow, "that they turn at all?"

_Tommy._--Because I see them move every night.

_Mr Barlow._--But how are you sure that it is the stars which move every
night, and not the earth itself?

Tommy considered, and said, "But then I should see the earth move, and
the stars stand still."

_Mr Barlow._--What, did you never ride in a coach?

_Tommy._--Yes, sir, very often.

_Mr Barlow._--And did you then see that the coach moved, as you sat
still, and went along a level road?

_Tommy._--No, sir; I protest I have often thought that the houses and
trees, and all the country, glided swiftly along by the windows of the
coach.

_Mr Barlow._--And did you never sail in a boat?

_Tommy._--Yes, I have; and I protest I have observed the same thing; for
I remember I have often thought the shore was running away from the
boat, instead of the boat from the shore.

_Mr Barlow._--If that is the case, it is possible, even though the earth
should move, instead of the stars, that you might only see what you do
at present, and imagine that the earth you are upon was at rest.

_Tommy._--But is it not more likely that such little things as the stars
and the sun should move, than such a large thing as the earth?

_Mr Barlow._--And how do you know that the stars and sun are so small?

_Tommy._--I see them to be so, sir. The stars are so small, that they
are hardly to be seen at all; and the sun itself, which is much bigger,
does not seem bigger than a small round table.

The day after this conversation, as the weather was bright and clear, Mr
Barlow went out to walk with Harry and Tommy. As by this time Tommy was
inured to fatigue, and able to walk many miles, they continued their
excursion over the hills, till at last they came in sight of the sea. As
they were diverting themselves with the immense prospect of water that
was before them, Mr Barlow perceived something floating at a distance,
so small as to be scarcely discernible by the eye. He pointed it out to
Tommy, who with some difficulty was able to distinguish it, and asked
him what he thought it was.

Tommy answered that he imagined it to be some little fishing-b