"The shells of hen-eggs, if properly filled and well secured against the penetration of the air, and exposed to solar rays, will ascend to the skies and sometimes suffer a natural change. And if the eggs of the larger description of swans, or leather balls stitched with fine thongs, be filled with nitre, the purest sulphur quicksilver, or kindred materials which rarify by their caloric energy, and if they externally resemble pigeons, they will easily be mistaken for flying animals."

Thus it would seem that, hunting back in history, there were three main ideas on which would-be aeronauts of old exercised their ingenuity. There was the last-mentioned method, which, by the way, Jules Verne partly relies on when he takes his heroes to the moon, and which in its highest practical development may be seen annually on the night of "Brock's Benefit" at the Crystal Palace. There is, again, the "tame goose" method, to which we must return presently; and, lastly, there is a third method, to which, as also to the brilliant genius who conceived it, we must without further delay be introduced. This may be called the method of "a hollow globe."

Roger Bacon, Melchisedeck-fashion, came into existence at Ilchester in 1214 of parentage that is hard to trace. He was, however, a born philosopher, and possessed of intellect and penetration that placed him incalculably ahead of his generation. A man of marvellous insight and research, he grasped, and as far as possible carried out, ideas which dawned on other men only after centuries. Thus, many of his utterances have been prophetic. It is probable that among his chemical discoveries he re-invented gunpowder. It is certain that he divined the properties of a lens, and diving deep into experimental and mechanical sciences, actually foresaw the time when, in his own words, "men would construct engines to traverse land and water with great speed and carry with them persons and merchandise." Clearly in his dreams Bacon saw the Atlantic not merely explored, but on its bosom the White Star liners breaking records, contemptuous of its angriest seas. He saw, too, a future Dumont circling in the air, and not only in a dead calm, but holding his own with the feathered race. He tells his dream thus: "There may be made some flying instrument so that a man sitting in the middle of the instrument and turning some mechanism may put in motion some artificial wings which may beat the air like a bird flying."

But he lived too long before his time. His ruin lay not only in his superior genius, but also in his fearless outspokenness. He presently fell under the ban of the Church, through which he lost alike his liberty and the means of pursuing investigation. Had it been otherwise we may fairly believe that the "admirable Doctor," as he was called, would have been the first to show mankind how to navigate the air. His ideas are perfectly easy to grasp. He conceived that the air was a true fluid, and as such must have an upper limit, and it would be on this upper surface, he supposed, as on the bosom of the ocean, that man would sail his air-ship. A fine, bold guess truly. He would watch the cirrus clouds sailing grandly ten miles above him on some stream that never approached nearer. Up there, in his imagination, would be tossing the waves of our ocean of air. Wait for some little better cylinders of oxygen and an improved foot-warmer, and a future Coxwell will go aloft and see; but as to an upper sea, it is truly there, and we may visit and view its sun-lit tossing billows stretching out to a limitless horizon at such times as the nether world is shrouded in densest gloom. Bacon's method of reaching such an upper sea as he postulated was, as we have said, by a hollow globe.

"The machine must be a large hollow globe, of copper or other suitable metal, wrought extremely thin so as to have it as light as possible," and "it must be filled with ethereal air or