Page:Popular Science Monthly Volume 28.djvu/18

10 acting constantly upon our silk, would be likely to rupture it; and when we consider that sudden gusts might readily increase the pressure five-fold, it will be admitted that terra firma would be decidedly safer, if less exciting.

More than all this, balloons as hitherto constructed are at best but temporary affairs, quickly losing their gas and buoyancy, expensive and unwieldy, and, however valuable for certain kinds of work, must be considered as simply floating, not flying machines. If we expect to gain the respect of the birds or butterflies, we must go to work in a much less clumsy way.

In the excitement following Montgolfier's invention, simple flying machines dropped out of sight almost entirely, and it was only after a long series of disappointing trials that the old ideas came to the surface again. The balloon craze, however, brought about a more careful study of aëronautics generally; but at the same time there has been and is a strong current of misguided thought and invention, particularly to be noticed in our Patent-Office reports.

Inventors of flying-machines, as a rule, belong rather in a lower class. Just as we still find old-new arrangements for producing perpetual motion, so in the attempts to fly the old story is repeated. The perpetual-motion man is likely also to know just how to make a successful flying-machine. lie only lacks the means. Still, particularly in England and on the Continent, many able men have been working intelligently, perseveringly, quietly. Before building a flying-machine they have thought best to study the examples Nature has provided, thinking that, while we need not necessarily imitate the mechanism, we may in this way get a better idea of the principles and action involved.

The broad principle governing either natural or artificial flight is quite simple, but the difficulty of applying it very great. Our flying machine, one that is much heavier than the air, and depending entirely upon its own power, in the first place, must be able by acting on the air to lift itself, and, while maintaining a position at any desired height, to propel itself forward. It must be prepared to encounter and take advantage of, and overcome currents of air sometimes hardly perceptible, sometimes perhaps a roaring gale—currents, too, not unlikely to suddenly change both in direction and velocity. It should be able to fly continuously for a long while, and should be tolerably safe.

On the water, if the machinery gives out, we can float or swim; but in the air any little difficulty of the sort would be likely to end unpleasantly. And even if, like a parachute, the machine could be made to drop slowly, in a brisk wind the final landing-place would for a while be a matter of uneasy conjecture.

It may easily be understood, then, that the problem is not a simple one, and yet, to a person watching, for example, the flight of a flock of gulls following in the wake of a steamer, the exquisite ease and grace and apparent simplicity of the movement are very striking. Sweeping