Page:Popular Science Monthly Volume 27.djvu/319

Rh The task was one which involved a heavy expenditure of money, aside from the time, labor, and thought bestowed by the inventor. He sought in vain to organize a company with a capital of two hundred thousand francs for the purpose of constructing an aërostat of three thousand cubic metres capacity; but the plan was not sufficiently promising of large dividends to be attractive to investors. No fortunes have been made thus far by the navigation of the air, and capitalists have not generally manifested a self-sacrificing spirit in behalf of pure science. The persevering aëronaut could find no one but his brother, M. Albert Tissandier, who was confident enough to join him in laying out capital for the promotion of what was generally regarded as a visionary scheme. The two brothers henceforward worked together, the one continuing to devote himself to the perfection of the electrical appliances on which reliance was to be placed, while the other, who is by profession an architect, gave his attention to the mechanical construction of the aërostat. M. Gaston Tissandier had found by experiments with his small aërostat that better results were to be had from a battery of cells, arranged in series, where a strong acid solution of potassium bichromate was the exciting liquid, than from a storage-battery the energy evolved during the first few hours being greater in proportion to the weight of the battery. He originated several ingenious contrivances by which great lightness was secured, and the liquid could be conveniently brought into contact with the zinc and carbon plates, or removed at will without disturbing the plates.

A Siemens electric motor was constructed, weighing but fifty-five kilogrammes. When excited by the current from a battery of twenty-four elements weighing one hundred and sixty-eight kilogrammes, this motor was found capable of doing work equivalent to that of twelve or fifteen men, that is, from seventy-five to one hundred kilogramme-metres per second, continued through three hours, the weight of battery and motor together being but little in excess of the weight of three men. Tissandier devised also important improvements in the method of generating pure hydrogen rapidly on a large scale. The ascensive force of this gas when pure is about seventy-five pounds per thousand cubic feet, or eleven hundred and eighty grammes per cubic metre; while that of coal-gas which has been most generally employed for ballooning purposes is not more than five eighths as much. By the substitution of hydrogen, the size, and consequently the expense, of the balloon is correspondingly diminished.

The aërostat constructed by M. Albert Tissandier is shown in Fig. 3. It is ninety-two feet long, thirty feet in its greatest diameter, with capacity of about thirty-eight thousand cubic feet, and ascensive power of twenty-eight hundred pounds. The propeller, nine feet in diameter, is in the rear of the cage. Above it, and farther back, is a triangular sail, to be manipulated as a rudder. On October 8, 1883, the first ascent was made. The air at the ground was calm, but