lo THE POPULAR SCIENCE MONTHLY. 



acting constantly upon our silk, would be likely to rupture it; and 

 when we consider that sudden gusts might readily increase the press- 

 ure five-fold, it will be admitted that terra Jirma 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 sur- 

 face again. The balloon craze, however, brought about a more care- 

 ful study of aeronautics generally ; but at the same time there has 

 been and is a strong current of misguided thought and invention, par- 

 ticularly to be noticed in our Patent-Oflice reports. 



Inventors of flying-machines, as a rule, belong rather in a lower 

 class. Just as we still find old-new arrangements for producing per- 

 petual 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 suc- 

 cessful flying-machine. He only lacks the means. Still, particularly 

 in England and on the Continent, many able men have been working 

 intelligently, perscveringly, 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 difticulty 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 per- 

 ceptible, sometimes perhaps a roaring gale — currents, too, not un- 

 likely 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 difticulty 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 



