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.