Among airships of the Allies, the French Speiss furnishes an example of the purely rigid design. Constructed on the plan of the German Zeppelin, its envelope has an inner wooden framework which holds it in place. The Speiss is a large dirigible, measuring about 450 feet. It carries two cars, and in each is a two-hundred horse power motor, giving it great speed.
PART III
CHAPTER I
Early Experiments with Heavier-than-Air Machines
For many centuries before the ascension of the first Montgolfier balloon, which, as we have seen, marked the beginning of aerial flight, men had dreamed of a different method of conquering the skies,—in fact, the very natural one suggested by the flight of birds. To build artificial wings was the ambition of many an old-time scientist. Yet practicable as the idea seemed, its working out was, as a matter of fact, beset with difficulties. The Montgolfier balloon rose in the air because it was lighter than air,—just as a piece of cork rises in water because it weighs less in proportion to its volume than the water. But a man equipped with wings is a fairly heavy object; where is the force that is to lift him and carry him soaring into the sky?
Unfortunately the early experimenters in aeronautics were not men who had had the long training in keen observation nor the groundwork of mechanical knowledge which would have fitted them for their task of devising a flying machine. They were dreamers and philosophers, often with very clever ideas about how man might succeed in flying. But the exact science of mechanics was yet unborn, and it was not until the nineteenth century, with its great advance in this direction, dawned, that the time was ripe for any measure of success. Still, in many old pictures and medieval manuscripts there are curious examples of the ideas of these old philosophers, designs which were never actually tried out, but which show the longing of men, even in those days, for the great adventure of sailing above the clouds.
All these strange theories of the middle ages were hampered by the superstition that there was some “magic” connected with the power of birds to fly. Cameras were unheard of, or it would have been a simple matter to have recorded on paper the actual motions of the bird's wings in order to study their significance. The astounding ease with which these little winged creatures were able to float across the heavens was indeed baffling; it was difficult to determine just how it was accomplished. Any one who watches the flight of a seagull realizes that here is an accomplished aeronaut, able to balance himself with perfect ease in the atmosphere, to mount upward on flapping wings, or, taking advantage of a rising air current which can support him, to float motionless with wings extended. All this requires an unusual amount of skill, particularly in balancing. Drop a piece of paper and watch how it turns and tumbles at every angle before it reaches the floor. That is just what a bird or an airplane has a tendency to do, and it takes a perfect system of control and a skilled pilot indeed, to keep it right side up.
The first idea, of course, for a heavier-than-air machine, was that of a pair of wings to be attached directly to the human body, and to be worked with the arms. As early as 1480 Leonardi da Vinci drew up a design for an apparatus of this sort. And the idea was not a bad one: it would have worked all very well had it not been for one small fact which the philosophers overlooked, that man is not provided with the powerful shoulder muscles such as the bird possesses for moving his wings.
Altogether, it was not until the nineteenth century that any real progress toward flight in a heavier-than-air machine was made. It came when experimenters began to investigate the definite laws of air resistance and air pressure which control the action of a bird just as they do the action of a kite. As a matter of fact, a bird, or an airplane, is nothing more than a complicated kite, controlled by an intelligence within itself, rather than by an operator standing on the ground and guiding it by means of a cord.