It had but one aperture, like the neck of a bottle, into which was fastened the stop-cock for the convenience of introducing and stopping-off the gas. It was constructed and inflated near the Place of Victories, in August, 1783, and after being inflated, which was then no easy task, occupying several days, it was removed on the morning of the 27th of that month, before daylight, to the Camp of Mars (two miles distant), the place appointed for its ascent. About five o'clock in the afternoon, it was released from its fastenings, and rose, in the presence of some hundred thousands of applauding spectators, to a height upward of 3000 feet; and, after remaining in the atmosphere for three-quarters of an hour, descended in a field near Gonesse, a village about fifteen miles distant from the Camp of Mars. This marks another important era in the history of aeronautics. The hydrogen-gas balloon, in the first place, is attended with less risk than the Montgolfiers' balloon, which requires the dangerous presence of a fire to preserve the air in a sufficiently rarified state; and, in the second place, it has a much greater ascending power than rarified air balloons of the same size, in consequence of its superior lightness. M. Charles and the two Messrs. Roberts now resolved to undertake an aerial excursion in a balloon of this description. With this view, the Messrs. Roberts formed one of silk, varnished with gum elastic, of a spherical shape, 27 feet in diameter, with a car suspended from it by several cords, which were fastened to a net drawn over the upper part of the balloon. To prevent the danger which might arise from the expansion of the gas under a diminished pressure of the atmosphere in the higher regions, the balloon was furnished with a valve, to permit the free discharge of gas, as occasion might require. The hydrogen gas with which it was filled was 5-1/4 lighter than common air, and the filling lasted several days. On December 17, 1783, M. Charles and one of the Roberts made their ascent from the garden of the Tuilleries, and rose to the height of 6000 feet. After a voyage of an hour and three-quarters, they descended at Nesle, a distance of 27 miles from the place of their departure. On their descent, M. Roberts having left the car, which lightened the vessel about 130 pounds, M. Charles reascended, and in twenty minutes mounted with great rapidity to the height of 9000 feet. When he left the earth, the thermometer stood at 47 degrees, but, in the space of ten minutes, it fell 21 degrees. On making this great and sudden transition into an atmosphere so intensely cold, he felt as if his blood had been freezing, and experienced a severe pain in the right ear and jaw. He passed through different currents of air, and, in the higher regions, the expansion of the gas was so great, that the balloon must have burst, had he not speedily opened the valve, and allowed part of the gas to escape. After having risen to the height of 10,500 feet,