CHAPTER FORTY NINE.
AEROSTATICS.
It is scarce possible to talk of a paper kite, without thinking of that other and greater aerostatic contrivance--a balloon.
Karl had thought of it, long before this time; and so had Caspar, just as long: for the kite had suggested it simultaneously to the minds of both.
It may be asked why they had not entertained the thought, and endeavoured to carry it into practical effect: since a balloon would have been far more likely to have delivered them out of their "mountain prison" than a paper kite?
But they _had_ entertained the thought--at least, Karl had done so--and examined it in all its bearings.

Caspar had 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.