y, 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 ba