Page:Popular Science Monthly Volume 64.djvu/147

Rh shattered to pieces, but beyond a few broken sticks it was as well and strong at the end of the journey as when it started.

The big tetrahedral kites, twelve feet and more on a side, look like awkward things to travel with or to store away, but they may be packed as handily and in as small compass as blankets or rugs. Each kite is made in collapsible sections, which open and then fold up, as shown in Fig. 12. Half a dozen large kites can in this way be carried in a trunk from place to place and put together in a few minutes.

The more recent experiments made have been to obtain a giant manlifting kite, or flying machine, that will rise from the surface of a lake. Any one who has ever watched a heavy bird rise from the ground has doubtless noticed that it runs along the ground for a few feet before it rises—the bird must acquire some momentum before its wings can lift its heavy body into the air. The natives of certain parts of the Andes understand this fact very well and by means of it catch the great Andean vultures. A small space is shut in with a high fence and left open at the top. Then a lamb or piece of carrion is placed on the ground inside. Presently a vulture sees the bait and swoops down upon it; but when once he has lighted on the ground inside he can not get out for he has no running space in which to acquire the momentum that is necessary before his wings can lift him. In the same way the first difficulty of all flying machines is to acquire the first momentum that will lift the machine into the air. To overcome this difficulty the flying machine inventor usually shoots his machine from a high platform which makes it necessary for the machine to rise immediately. But if the flying machine can not start in a natural way the chances are its method of working is not right and it is doomed to failure. And even if a machine could fly perfectly after it had been started how could it get up again if it came down for food or fuel at some point where there was no platform and starting