“Toward the end of Charlemagne’s reign, persons who lived near Mount Pilate in Switzerland, knowing by what means pretended sorcerers traveled through the air, resolved to try the experiment, and compelled some poor people to ascend in an aërostal. This descended in the town of Lyons, where they were immediately hurried to prison, and the mob desired their death as sorcerers. The judges condemned them to be burned; but the Bishop Agobard suspended the execution, and sent for them to his palace, that he might question them. They answered: ‘Qu’ils sont du pays meme, que des personnes de consideration les ont forcés de se laisser conduire, leur promettent qu’ils verroient des chose merveilleuses; et qu’ils sont veritablement descendu par l’air.’ Agobard, though he could not believe this fact, gave credence to their innocence, and allowed them to escape. On this occasion he wrote a work on the superstition of the time, in which he demonstrated the impossibility of rising in the air; that it is an error to believe in the power of magic; and that it has its existence in the credulity solely of the people.”
One of the first men to make an aërial model like a fire balloon was the celebrated Brazilian, Bartholomeo-Lourenco de Gusmao, who in his day was nicknamed the “flying man,” and who is reported to have made a remarkable experiment in aërial locomotion at Lisbon. The following account of it is found in a manuscript of Ferreira:
“Gusmao made his experiment on August 8, 1709, in the court of the Palace of the Indies, before his majesty and a large and distinguished audience, with a globe which lifted itself softly to the height of the hall of the Ambassadors, then descended in like manner. It was borne up by certain materials which burned and which the inventor himself had ignited.”
All the details of this description, which was written a generation or more before the Montgolfier experiment, suggest at once a hot-air balloon. But a note printed in 1774 and cited by Cavallo explains that the globes must have been transported by gas. It is certain that early in 1709 Gusmao applied to the King for a patent and sole right to some such invention, desiring an injunction and severe penalty against all infringements. The application sets forth a machine capable of journeying through the air faster than over land or sea, competent to carry messages five or six hundred miles a day to troops, or the most distant countries, and even adequate to explore regions about the poles. Quite a modern promoter Señor Gusmao. The King in reply issued the following decree:
“Agreeably to the advice of my council, I order the pain of death against the transgressor. And in order to encourage the suppliant to apply himself with zeal toward improving the machine which is capable of producing the effects mentioned by him, I also grant him the first Professorship of Mathematics in my University of Coimbra, and the first vacancy in my College of Barcelona, with the annual pension of 600,000 reis during his life.”
The “patent” seemed liberal enough, and yet Gusmao never resumed his aërial experiments. He was accused of magic, and may have feared persecution on that account; accordingly he engaged in naval construction till 1724, when he left Portugal.
The first vacuum balloon was proposed by the Jesuit father, Francis Lana, and described in his book Podromo dell’Arte Maestra Brecia, which appeared in 1670. Though not a practical project like Gusmao’s, it was very ingenious, and marks an interesting phase in the evolution of the fundamental idea of the air ship, or “balloon” as it was called by the inventor, who then coined the word now in common use. Lana proposed to use four copper spheres each 25 feet in diameter and 1/225 inches in wall thickness, quite well exhausted of air, to give ascensional force which he computed at 1,200 pounds aggregate for the four spheres. From these he would suspend the passengers in a boat having a mast and sail to propel the ship in time of favorable wind. Having computed the buoyancy according to well-known physical laws, he could see no possible objection to his project “unless,” he writes, “it be that God would never permit this invention to be practically applied, in order to prevent the consequences that would ensue therefrom in the civil and political government of men.”
Fig. 4.—Lana’s Proposed Vacuum Balloon.
Of recent years inventors having less delicate scruples about embarrassing Providence, have revived Lana’s project with improvements. It has been proposed to replace the sail by a motor-driven propeller, and to ensure the hull against collapse from the prodigious external air pressure—a ton per square foot—by ample internal bracing. Even within the past twelve months this scheme has been soberly advocated by several technical journals and by the author of an elaborate book on aërial warfare. To a mathematician this is amusing, when not too pathetic; for it can be rigorously proved that no vacuum balloon of present day material, whatever its design, can possibly resist crushing if made light enough to float.