speed, with which the screw is driven, is increased. The screw in this manner is self-adjusting, and extracts a large percentage of propelling power, with very little force and surprisingly little slip. A similar result is obtained if two finely graduated angularshaped gutta-percha or steel plates be placed end to end and applied to the water (vertically or horizontally matters little), with a slight sculling figure-of-8 motion, analogous to that performed by the tail of the fish, porpoise, or whale. If the thick margin of the plates be directed forwards, and the thin ones backwards, an unusually effective propeller is produced. This form of propeller is likewise very effective in air. CONCLUDING REMARKS. FROM the researches and experiments detailed in the present volume, it will be evident that a remarkable analogy exists between walking, swimming, and flying. It will further appear that the movements of the tail of the fish, and of the wing of the insect, bat, and bird can be readily imitated and reproduced. These facts ought to inspire the pioneer in aërial navigation with confidence. The land and water have already been successfully subjugated. The realms of the air alone are unvanquished. These, however, are so vast and so important as a highway for the nations, that science and civilisation equally demand their occupation. The history of artificial progression indorses the belief that the fields etherean will one day be traversed by a machine designed by human ingenuity, and constructed by human skill. In order to construct a successful flying machine, it is not necessary to reproduce the filmy wing of the insect, the silken pinion of the bat, or the complicated and highly differentiated wing of the bird, where every feather may be said to have a peculiar function assigned to it; neither is it necessary to reproduce the intricacy of that machinery by which the pinion in the bat, insect, and bird is moved: all that is required is to distinguish the properties, form, extent, and manner of application of the several flying surfaces, a task attempted, however imperfectly executed, in the foregoing pages. When Vivian and Trevithick devised the locomotive, and Symington and Bell the steamboat, they did not seek to reproduce a quadruped or a fish; they simply aimed at producing motion adapted to the land and water, in accordance with natural laws, and in the presence of living models. Their success is to be measured by an involved labyrinth of railway which extends to every part of the civilized world; and by navies whose vessels are despatched without trepidation to navigate the most boisterous seas at the most inclement seasons. The aëronaut has a similar but more difficult task to perform. In attempting to produce a flying-machine he is not necessarily attempting an impossible thing. The countless swarms of flying creatures testify as to the practicability of such an undertaking, and nature supplies him at once with models and materials. If artificial flight were not attainable, the insects, bats, and birds would furnish the only examples of animals whose movements could not be reproduced. History, analogy, observation, and experiment are all opposed to this view. The success of the locomotive and steamboat is an earnest of the success of the flying machine. If the difficulties to be surmounted in its construction are manifold, the triumph and the reward will be correspondingly great. It is impossible to over-estimate the boon which would accrue to mankind from such a creation. Of the many mechanical problems before the world at present, perhaps there is none greater than that of aërial navigation Past failures are not to be regarded as the harbingers of future defeats, for it is only within the last few years that the subject of artificial flight has been taken up in a true scientific spirit. Within a comparatively brief period an enormous mass of valuable data has been collected. As societies for the advancement of aëronautics have been established in Britain, America, France, and other countries, there is reason to believe that our knowledge of this most difficult department of science will go on increasing until the knotty problem is finally solved. If this day should ever come, it will not be too much to affirm, that it will inaugurate a new era in the history of mankind; and that great as the destiny of our race has been hitherto, it will be quite out-lustred by the grandeur and magnitude of coming events. INDEX. AERIAL creatures not stronger than terrestrial ones, Air cells in insects and birds not necessary to flight, Albatross, flight of, compared to compass set upon gimbals, Amphibia have larger travelling surfaces than land animals, but less than aërial ones, Artificial fins, flippers, and wings, how constructed, Artificial wings, Borelli, PAGE 13 92 209 115 199 8 14 219 Do. Marey, 226 how to construct to evade the superimposed air during 241 Do. can create currents and rise upon them, 253 Do. can be driven at any speed; can make new currents 251, 255 Do. as a propeller and aërial screw, -256 Do. compound rotation of: the different parts of the wing travel at different speeds, 252 Do. necessity for supplying root of, with elastic structures, 247 Body and wing reciprocate in flight, and each describes a waved track, Bones, Bones of the extremities twisted and spiral, Bones of wing of bat-spiral configuration of their articular surfaces, CHABRIER'S artificial wings, 190 205 12 ELYTRA or wing cases and membranous wings, FEATHERS, primary, secondary, and tertiary, Fins, flippers, and wings form mobile helices or screws, Flight the poetry of motion, Flight the least fatiguing kind of motion, Flight under water, Flight of the flying-fish, Flight, horizontal, in part due to weight of flying mass, Flight-the regular and irregular, Flight-how to ascend, descend, and turn, Flight of birds referrible to muscular exertion and weight, Flying machine, Henson, Do. Do. Do. Do. Do. A flying machine possible, Forces which propel the wings of insects, bats, and birds, 186, 189 8, 104, 165 18 18 HISTORY of the figure-of-8 theory of walking, swimming, and flying, . JOINTS, KITE-LIKE action of the wings, Kite-how kite formed by wing differs from boy's kite, LAWS of natural and artificial progression the same, Lever the wing one of the third order, Levers, the three orders of, Life linked to motion, Lifting capacity of birds, Ligaments, Ligaments, elastic, position anal action of, in wing of pheasant, snipe, Ligaments, elastic, more highly differentiated in wings which vibrate Motion associated with the life and well-being of animals, Motion, natural and artificial, |