ng--
a sort of grate or fire-basket suspended below. Now, even if we had the
silk to make the great spherical bag, how could we make a fire-basket
without iron?"

"We should not need the fire-basket you speak of. That is only
required, when you design to keep your balloon some length of time in
the air. If you only wish to make a short ascent, once filling the bag
with hot air is sufficient; as it would be for us here. Even if we
wanted a suspended grate, surely, brother, you have enough ingenuity to
get over such a trifling difficulty as that?"

"Well, I'm not so sure that I could. How would you get over it?"

"Why, by making a common basket, and lining it with clay. That would
carry fire, as well as a vessel of either cast or wrought iron--at least
sufficient to serve for a short excursion such as we should care to
make. Now-a-days, fire is not used for inflating balloons. Inflammable
gas has been found to be far superior for this purpose; but as we have
no such thing in stock, we should have to proceed on the old original
plan--that employed by the brothers Montgolfier--the first inventors of
the balloon."

"You think, then, that the fire apparatus could be dispensed with, if we
could only discover some material that would make the great globe-shaped
bag to contain the heated air?"

"Ay," replied Karl; "think of something to do that, and I promise to
make you a balloon."

Thus challenged, Caspar set his wits to work; and for a long while he
sat in silence, as if buried in some very profound speculation.
Probably, there was no material substance in that valley that did not
pass in review before the retina of his mental vision; and all were
considered in turn.

"It must be light, air-tight, and strong?" asked he, at length, as if
there was something in his thoughts possessing these three requisites.

"Light, air-tight, and strong," answered Karl, simply repeating his
words.

"The two last I am sure of," rejoined Caspar. "Of the first only have I
my doubts."

"What is it?" asked Karl, in a tone that betrayed his interest in what
Caspar had said.

"Eel-skins!" was the laconic answer.

CHAPTER FIFTY.

THE SKIN BALLOON.

"Eel-skins," said Caspar, repeating the phrase, as he saw that Karl
hesitated before pronouncing an opinion. "Don't you think they would
do?"

Karl had it on the tip of his tongue to cry out--"The very thing!" but
something withheld him from making this unqualified decla