d not live in them,
but they go up _by means_ of them."

"How?" said Nathan.

"Why, they have a kind of basket, which hangs down below the balloon,
and they get into that."

"I knew they could not get into the balloon," said Nathan.

"Then you have had a dispute about it," said his mother.

"Why,--yes," said Nathan, with hesitation, "we disputed a little."

"I am sorry to hear that," said his mother, "for disputing seldom does
any good. The fact is, however, that men have often been carried up by
balloons, but they never get into them. They could not live in them.
They could not breathe the kind of air which balloons are filled with."

"It is hot air," said Nathan.

"No," said his mother, "the kind of balloon which your father told you
of was filled with hot air; but the balloons which people generally use
to go up with, are filled with another kind of air, which is very light
when it is cool. They make an enormous bag of silk, and fill it with
this light air, which they make in barrels; and then, when the bag is
filled, it floats away above their heads, and pulls hard upon the
fastening. There is a net all over it, and the ends of the net are drawn
together below, and are fastened to the basket, or car, where the man is
to sit. When it is all ready, the man gets into the car, and then they
let go the fastenings, and away the great bag goes, and carries the man
with it, away up into the air."

"And then how does he get down?" said Nathan.

"Why, he can open a hole in the bag, and let some of the light air out;
and then he begins to come down slowly. If he comes down too fast, or if
he finds that he is coming into the water, or down upon any dangerous
place, there is a way by which he can make his balloon go up again."

"What way is it, aunt?" said James.

"Why, he has some bags of sand in his balloon," said his aunt; "and the
balloon is made large enough to carry him and his sand-bags too. Then,
if he finds that he is coming down too fast, he just pours out some of
his sand, and that makes his car lighter; and so the balloon will carry
him up again."

"That's a good plan," said Rollo.

"Yes," said his mother; "the reason why he takes sand is, because that
will not hurt any body by falling upon them. If he should take stones,
or any other heavy, solid things, and should drop them out of his car,
they might possibly fall upon some body, and hurt them. So he takes sand
in bags, and, when he wants to lighte