The Tissandier brothers of France moved an airship by means of electricity generated by bichromate of potash cells. Redard and Krebs of Germany also attempted the feat of governing the motion of a huge gas bag through the circumambient atmosphere. Electricity from batteries, power from steam and gas engines, and finally energy from the very air itself, represents the efforts made to build a useful, reliable and consequently durable airship. Like an ignis fatuus it has been dancing before the eyes of the public for more than a century as a thing apparently within our clutch, yet constantly evading us. But the record of advancement in this field has at least been the record of engineering efforts to create a definite machine.
From this standpoint the air-ship problem is no longer confined to any haphazard class of experimenters in the strict sense of the word. But it may be regarded as a possible development in the field of mechanical or electrical engineering. It may be expected to develop greatly in the very near future; and it is therefore imperative to keep in touch with its various phases of growth in order to appreciate the science, the art and the logic which culminate in its successful issue. Electricity has had a hand in its development, though of late it has been superseded by the gasoline and steam engine, for the simple reason that, pound for pound, including the source of power-fuel and water or both-the motor and batteries are out of the race. As an ignition feature of the gasoline engine, electricity cannot be safely dispensed with. With all this preamble though, the problem arranges itself into three parts. The gas bag providing the flo-tative force coming first, and which though strongly made today does not differ fundamentally from that sent up in the air by the Montgolfier brothers many years ago.
The steerable or dirigible balloon comes next; of which, perhaps, the Santos Dumont type is most characteristic at the present time, and to which the ship of the Tissandier brothers belonged. The last is of the aeroplane type, developed to a remarkable extent by Prof. Langley of the Smithsonian Institution. Thus the air-ship has passed through three stages of growth, which can be divided, however, into two distinct fields of experiment. The older field follows along the lines indicated by the use of a self-flotative body such as a balloon. The newer field takes the bird as a model and attempts success with a non-flota-tive but withal self-supporting machine, essentially heavier than its own bulk of air.
An investigation of this latter class of machines discloses one elusive feature. They are able to rise into the air only in the teeth of the wind. The supporting element is therefore derived from this source, and according to such authorities we have, birds themselves, of the so-called soaring class, rise or support themselves in this manner. The swift winging class, however, represent a curious anomaly, in that their weight represents, a much greater wing surface than the heavier soaring birds. To quote from R. Von Linden-fields's remarks in the conclusion of an article by him, whose data was obtained from measurements of the weight and wing surface of flying creatures of all descriptions and embodied in an article called "Relation of Wing Surface to. Weight" : "According to the foregoing, if the combined weight of the body and the mechanical flying apparatus amounts to 90 kilograms, 198 pounds, in order to sail like an albatross a man would require 90,000 times 30, or 2,700,000 square millimeters of wing surface; that is to say, two wings furnishing together 2.7 square meters, 20 square feet of surface."
In conclusion it may be stated that the value of such information is entirely dependent upon the drift of experimentation. At present the imitation of the bird is the basis of all activity in this field. That it is a heavy body that readily supports itself in the free air with little effort is obvious. For this reason we must look to air currents for the source of its flotative power, more than its wing effort. But the fact that it springs into the air when it operates its wings-and if a soaring bird, does not stop flapping until it reaches a certain point in the air-shows clearly that the power of a flying machine will only be greatly called upon to raise it into the air to a certain height. At this point the navigator will be required to find an air current to bear his ship, and in particular will be forced to exercise skill to preserve its position in space.
Along linese lines, aerial navigation will probably be carried out, when the secret of construction and control are a little better crystalized than at present.