Page:Popular Science Monthly Volume 44.djvu/773

This page has been proofread, but needs to be validated.

Chicago at the World's Congress of Aeronautics. This model was fifteen feet long, with two transverse aeroplanes forty feet from tip to tip. Whether it was so exhibited or not I do not know. Maxim, it is said, is now constructing a flying machine on a large scale in London, but has not attempted yet to launch it. In both of these the aëroplane slightly inclined is the main reliance for sustaining when once in motion; so that the whole power of the engine and propellers is concentrated on rising and progress through the air.

Now, in the light of these experiments, what may we reasonably expect in the near future?

There are many difficulties in the way of success, which, of course, these men clearly see and will try to provide for. These are mainly three, viz.: (1) Difficulty of rising; (2) stability in progress; and (3) safety in alighting. We take these in succession.

1. Rising.—Every word I have said in my previous paper, only modified as to limit of weight, applies here still and without abatement. It seems to be impossible for any machine, natural or artificial, of greater weight than at most a few hundred pounds, to lift itself straight up in the air, or even to maintain itself in the same place like a hovering bird, by the force of propellers alone and without the aid of a balloon. Therefore, there must be some device other than, or in addition to, propellers to raise the machine in the act of starting. But observe, I said straight up. Many birds can not rise so. They must rise at very gentle incline. They must get onward motion before their wings can get full effect on the air. It is said that the mode of taking the condor is to build a pen, say, forty to fifty feet in diameter and six feet high, and put a carcass in the middle of it. The condor alights, but can not again rise at an angle which will take him over the fence. Many heavy-bodied, short-winged ducks rise from the water at so small an angle that they must use both feet and wings for thirty to forty feet in order to get onward motion enough to give effectiveness to their wings by coming in contact with larger masses of still air, as already explained. It follows, therefore, that the flying machine must have some station device to start it. It may be an elevator, but more probably it will be machine rollers on a railway. With aëroplane spread and slightly inclined and propellers directed a little backward, velocity might be got sufficient to sustain and finally with the help of the propellers to raise the machine. As far as I can learn, this is the plan of Maxim.

Viewed in the light of the new principle, there is certainly nothing impossible in this. But every machine is liable to accidents. It is absolutely necessary that we should be able to stop and go on again. Suppose in mid-flight anything should go