The Problem of Flight.
One of the most promising fields for the application of motive power would seem to be that of the air around us. Professor S. P. Langley, Secretary of the Smithsonian Institution at Washington, since the beginning of 1887, has been making experiments addressed to solving the great problem of aerial flight. In a monograph, recently published by the Smithsonian, he describes and illustrates his experiments in a most interesting way. In imitating with metal planes the speed of rapid flight. Professor Langley came upon its secret, a secret which lay hidden when only locomotion on land and water has been studied. He has discovered that the swifter a bird can fly the less effort does it put forth in suporting itself in the air, this for the same reason that a plane is retarded in falling through the air in proportion to the rapidity of its ‘atcral motion. This relaiding effect increases as the width of a plane is augmented as compared with its length. Professor Langley’s experiments completely subvert the theoretical calculations of Sir Isaac Newton in the I’rincipia, and establish that in certain circumstances the supporting power of a plane can be twenty times that computed according to the Newtonian formula. With wing planes loaded so as to weigh 209 pounds, Professor l .angiey has ascertained that one horse-power is adequate to both its support in air and its movement through it at the rate of forty-tive miles an hour. At higher speeds less power would be required up to a limit not readied in experiment. Now, as engines have been made to weigh less than ten pounds per horse-power, and can be operated for five hours with ten pounds of oil, we would seem to be on the eve of mastering the field of air by a power which, after all, is freely exercised by every house fly and sparrow. All that needs lobe known to make mechanical flight an engineering success is a right method of constructing the necessary machinery of securing its safe ascent and descent, and of applying the motive power with economy. And here must come in an appeal to nature, and instantaneous photography is enlisted to show precisely how a bird undulates its wings from moment to moment, so as to exert a power which has ever tilled mankind with envy. And far below the bird in rank are creatures whose capacities, if successfully imitated, would greatly improve the lot of man. When the wax candle gave way to the gas jet, light brought with it only three-fourths as much heat as before. When the gas jet in turn makes way for the incandescent lamp, fed by the electric current, the accompaniment of useless heat falls one-twenty-third as much as, formerly. In some of the best arc lamps it is estimated that the heat rays have been so reduced as to represent no more units of force than the rays of light. One-half, therefore, of jierfect efficiency has been attained. Far otherwise is it with the incandescent filament, whose radiance means but one part light to eleven parts heat. This loss, be it remembered, has to be paid in addition to the heavy tax levied by the steam engine as it converts its fuel into motive power, for the dynamo. The electrician, for all his complexity of appearance, is still far behind certain lowly insects as a light giver.
In the glowworm, and in the fire fly, especially in the splendid species in Cuba, Professor S. P. l.angiey has found that light is emitted with no wasteful partnership whatever with rays of heat. How soon will genius, keen of eye, skillful of hand, read the secret of this tiny craftsman and translate it into an engine for the illumination of the world?