ad permitted it to pass out of
his mind, under the impression that _they could not make a balloon_; and
Karl had arrived at the same conclusion; but only from a belief that
they _had not the materials_ with which to make one. Given the
materials, Karl felt quite equal to the construction of a balloon--a
rude one, it is true; but one which might have served the purpose for
which they required it.

During the days when they had been occupied in making the paper-bird, he
had given his thoughts a good deal to this subject; for, to say the
truth, he had never been very sanguine about the success of the kite
experiment. He had pondered long and patiently on the subject of
balloons--endeavouring to recall to mind what little he had studied of
aerostatics--and had mentally examined all the material objects within
reach, in the hope of discovering some substance out of which one might
be constructed.

Unfortunately, he had not been able to think of anything that appeared
to be suitable. The daphne paper--even had it been in abundance--would
not do: for paper of itself, however close in texture, is not strong
enough to withstand the pressure of the outside air--that is, in a
balloon of sufficient size to carry any considerable weight. But it was
of no use to talk of paper: since there was not enough; and Karl had
given over thinking of a balloon: because there was nothing within reach
likely to serve for its construction.

He knew that that great sphere would require to be air-proof. He had
thought of the skins of animals; but such of these as might have been
obtained in sufficient quantity, were entirely too thick and heavy to
make the covering of a balloon. The hemp, of which there _was_ an
abundance, might be woven into a cloth, and then coated over by gum
obtained from some tree; for in the valley were several species of
gum-exuding trees. But the question was, could they manufacture a cloth
out of hemp that would be light enough when thus coated over? It was
very doubtful whether they could--at all events they would have to
practise the weaving trade for a long time, before they should arrive at
a sufficient expertness to accomplish such a feat. The plan was too
unpromising to be seriously entertained; and Karl had dismissed it,
along with the whole subject of the balloon.

That had been previous to the experiment of the kite, and its
unfortunate ending. But now that all hope from this quarter had been
brought