"Don't bother yourself about that, Sarah," said Sammy. "We'll
have all the air we want; of course we would not start without
thinkin' of that."

"I don't know," said Sarah. "It's very seldom that men start off
anywhere without forgettin' somethin'."

"Let us take our seats, Mrs. Block," said Mr. Gibbs, "and I will
set your mind at rest on the air point. There are a great many
machines and mechanical arrangements on board here which of course
you don't understand, but which I shall take great pleasure in
explaining to you whenever you want to learn something about them.
Among them are two great metal contrivances, outside the Dipsey and
near her bows, which open into the water, and also communicate with
the inside of her hull. These are called electric gills, and they
separate air from the water around us in a manner somewhat
resembling the way in which a fish's gills act. They continually
send in air enough to supply us not only with all we need for
breathing, but with enough to raise us to the surface of the water
whenever we choose to produce it in sufficient quantities."

"I am glad to hear it," said Mrs. Block, "and I hope the machines
will never get out of order. But I should think that sort of
air, made fresh from the water, would be very damp. It's very
different from the air we are used to, which is warmed by the sun
and properly aired."

"Aired air seems funny to me," remarked Sammy.