part farther and farther from us, at last it would appear no bigger
than one of those twinkling stars that you see at so great a distance
above your head.

_Tommy._--That I perfectly comprehend.

_Mr Barlow._--But if, on the contrary, one of those twinkling stars were
to approach nearer and nearer to where you stand, what do think would
happen? Would it still appear of the same size?

_Tommy._--No, sir. The ship, as it came nearer to us, appeared every
moment larger, and therefore I think the star must do the same.

_Mr Barlow._--Might it not then appear as big as the sun now does, just
as the sun would dwindle away to the size of a star, were it to be
removed to a still greater distance?

_Tommy._--Indeed I think it might.

_Mr Barlow._--What, then, do you imagine must happen, could the sun
approach a great deal nearer to us? Would its size remain the same?

_Tommy._--No; I plainly see that it must appear bigger and bigger the
nearer it comes.

_Mr Barlow._--If that is the case, it is not so very certain that the
earth we inhabit is bigger than the sun and stars. They are at a very
great distance from us; therefore, if anybody could go from the earth
towards the sun, how do you think the earth would appear to him as he
journeyed on?

_Tommy._--Really I can hardly tell.

_Mr Barlow._--No! Why, is it not the same thing, whether an object goes
from you, or you from the object? Is there any difference between the
ship sailing away from us, and our walking away from the ship?

_Tommy._--No, sir.

_Mr Barlow._--Did you not say that if the sun could be removed farther
from our eyes, it would appear less?

_Tommy._--To be sure it would.

_Mr Barlow._--Why, then, if the earth were to sink down from under our
feet, lower and lower, what would happen? Would it have the same
appearance?

_Tommy._--No, sir; I think it must appear less and less, like the ship
that is sailing away.

_Mr Barlow._--Very right, indeed; but now attend to what I asked you
just now. If a person could rise slowly into the air, and mount still
higher and higher towards the sun, what would happen?

_Tommy._--Why the same as if the earth were to sink from under us; it
would appear less and less.

_Mr Barlow._--Might not the earth then at least appear as small as the
sun or moon does?

_Tommy._--I can hardly conceive that, and yet I see it would appear less
and less the farther we went.

_Mr Barlow._--Do you remember what happened to