THE BALLOON
Two very decided failures, of late,—those of Mr. Henson and Sir George Cayley,—had much weakened the public interest in the subject of aerial navigation. Mr. Henson's scheme (which at first was considered very feasible even by men of science) was founded upon the principle of an inclined plane, started from an eminence by an extrinsic force, applied and continued by the revolution of impinging vanes, in form and number resembling the vanes of a windmill. But, in all the experiments made with models at the Adelaide Gallery, it was found that the operation of these fins not only did not propel the machine, but actually impeded its flight. The only propelling force it ever exhibited, was the mere impetus acquired from the descent of the inclined plane, and this impetus carried the machine farther when the vanes were at rest, than when they were in motion—a fact which sufficiently demonstrates their inutility, and in the absence of the propelling, which was also the sustaining power, the whole fabric would necessarily descend. This consideration led Sir George Cayley to think only of adapting a propeller to some machine having of itself an independent power of support—in a word, to a balloon; the idea, however, being novel, or original, with Sir George, only so far as regards the mode of its application to practice.