"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 declaration.
"They might--it is possible they might," said he, apparently debating
the question within himself--"just possible; and yet I fear--"
"What do you fear?" asked Caspar.
"Do you think they would not be strong enough?"
"Strong enough," replied Karl. "That's not what I fear."
"The air can't pass through an eel-skin?"
"No--not that."
"At the seams, perhaps? We can stitch them neatly; and then gum them
over at the joinings. I'll warrant Ossaroo can sew like a shoemaker."
The shikaree could do all that. Karl knew it. It was not there the
difficulty lay.
"The weight, then?" pursued Caspar interrogatively.
"Precisely that," answered Karl; "I fear they will be too heavy. Bring
one, Ossaroo; and let us have a look at it."
The shikaree rose from his seat; and going into the hovel, returned
presently--bringing back with him a long shrivelled object, which any
one could tell to be a dried eel-skin.
There were many like it inside: for they had carefully preserved the
skins of the eels they had caught, induced to do so by a sort of
presentiment, that some day they might find a use for them. In this
case their prudent providence was likely to prove of service to them.
Karl took the skin; and, holding it out on the palm of his hand,
appeared to make an estimate of its weight. Caspar watched his
brother's countenance, and waited to hear what he would say; but Karl
only expressed himself by a doubtful shake of the head, which seemed to
show that his opinion was _against_ the eel-skins.
"They might be made much lighter, I fancy," suggested Caspar: "scraping
would do a deal for them; and by the way, why would not boiling make
them light enough? It would take all the fatty, oily substance out of
them."
"There's something in what you say," rejoined Karl, apparently impressed
by the last suggestion. "Boiling might render them a good deal lighter.
We can easily try it."
As Karl said this, he proceeded to the boiling spring, and plunged the
eel-skin under the water. There it was permitted to remain for about
half an hour, when it was taken out; and, after being scraped with the
blade of a knife, was spread upon a rock, under the sun, where it would
soon get thoroughly dry.
They all waited patiently for the completion of this process. The
result was of too interesting a character to allow of their occupying
themselves with anything else.
In due time the eel-skin had become sufficiently dry, to be submitted to
examination; and Karl, once more taking it up, balanced it upon his
palm.
Tested, even in this inexact fashion, it was evidently much lighter than
before; and, by the gratified look with which the philosopher regarded
it, he appeared to be much better satisfied with its weight. Still,
however, he was not sanguine: as his words testified. They were almost
a repetition of what he had said before.
"It may do--it is just possible. At all events, there can be no harm in
trying. Let us try it, then."
To say, "Let us try it," meant the same as to say, "Let us make the
balloon." The others understood that; and of course acquiesced in the
determination.
As there was nothing to interfere with the immediate commencement of the
work, they resolved to set about it at once; and in fact did set about
it without farther delay.
The number of eel-skins on hand, though very considerable, would not be
near enough for covering a balloon; and therefore Ossaroo went to work
with his hooks and lines to catch a few hundreds more. Karl was able to
tell how many it would take; or he could at least make an estimate
sufficiently exact for the purpose. He designed a balloon of twelve
feet diameter: for he knew that one of less size would not have power
enough to carry up the weight of a man. Of course, Karl knew how to
calculate the surface of a sphere whose diameter should be twelve feet.
He had only to multiply the diameter on the circumference; or the square
of the diameter on the fixed number 3.1416; or find the convex surface
of the circumscribing cylinder; or else find four times the area of a
great circle of the said sphere. Any one of these methods would give
him the correct result.
On making the calculation, he found that a sphere of 12 feet diameter
would have a surface of 452 square feet, within a trifling fraction.
Therefore 452 square feet of eel-skins would be required to cover it.
In other words, that quantity would be required to make the balloon.
As the eels happened to be of large size--most of them being over a yard
in length, and full four inches in average girth--the skin of one when
spread out would yield about a square foot of surface. Taking large and
small together--and allowing for waste, the heads and tails that would
have to be chopped off--Karl calculated that he would get nearly a
square foot each out of the eels; and that about five hundred skins
would make the balloon bag. But as they would have to be cut
occasionally with a slant, in order to get the globe shape, perhaps a
few more would be needed; and therefore Ossaroo was to keep his baits in
the water, until the requisite number of eels should be hooked out of
it.
Ossaroo had another department assigned to him besides catching the
fish; and one that took up more of his time: since the baiting of the
hooks, and looking after them, required only his occasional attention.
Spinning the thread by which the skins were to be sewed together, was a
much more delicate operation: since in these both strength and fineness
were absolutely necessary. But as Caspar had said, Ossaroo was an adept
with the distaff; and several large skeins of the finest twist were soon
turned off from his nimble fingers.
When enough thread had been thus produced, Ossaroo proceeded to making
the cords and stronger ropes, that would be needed for attaching the
"boat"--as well as to hold the balloon in its place, while being got
ready for its ascent.
Caspar's employment was--first, the skinning of the eels; and afterwards
the scraping, boiling, and drying of the skins; while Karl, who acted as
engineer-in-chief, besides giving a general superintendence to the work,
occupied himself in imparting the final dressing to the material, and
cutting it into such shapes, that it could be closely and conveniently
stitched together.
Karl had also made an excursion into the forest, and brought back with
him large quantities of a gum, which he had extracted from a tree of the
genus _ficus_--a sort of _caoutchouc_--which is yielded by many species
of _ficus_ in the forests of the Lower Himalayas. Karl had gone in
search of this substance, because he knew it would be required for
paying the seams, and rendering them air-tight.
When they had pursued their various avocations for about a week, it was
thought that material enough of every kind was collected and made ready;
and then Ossaroo was set to stitching. Fortunately, they were provided
with needles: for these had formed a part of the _accoutrement_ of the
plant-hunters--when originally starting upon their expedition.
As neither Karl nor Caspar had any experience in handling such sharp
tools, the sewing had all to be done by Ossaroo; and it took another
full week to accomplish this Sartorean task.
At the end of that time, it was fully accomplished and complete; and the
huge bag was ready to receive its coat of gum varnish. A day sufficed
for "paying;" and nothing more remained but to attach the "boat," or
"car," that was to carry them aloft in their daring flight into the
"azure fields of air."