On the day after the experiment of the Champ de Mars (27th of August), Professor Charles--who had already acquired celebrity at the Louvre, by his scientific collection and by his rank as an official instructor--and the Brothers Robert, mechanicians, were engaged in the construction of a balloon, to be inflated with hydrogen gas, and destined to carry a car and one or two passengers. For this ascent Charles may be said to have created all at once the art of aerostation as now practiced, for he brought it at one bound to such perfection that since his day scarcely any advance has been made upon his arrangements. His simple yet complete invention was that of the valve which gives escape to the hydrogen gas, and thus renders the descent of the balloon gentle and gradual; the car that carries the travellers; the ballast of sand, by which the ascent is regulated and the fall is moderated; the coating of caoutchouc, by means of which the material of the balloon is rendered airtight and prevents loss of gas; and, finally, the use of the barometer, which marks at every instant, by the elevation or the depression of the mercury, the position in which the aeronaut finds himself in the atmosphere. Charles created all the contrivances, or, in other words, all the ingenious precautions which make up the art of aerostation. On the 26th of November, the balloon, fitted with its network, and having the car attached to it, was sent away from the hall of the Tuileries, where it had been exhibited. The ascent was fixed for the 1st of December, 1783, a memorable day for the Parisians. At noon upon that day, the subscribers, who had paid four louis for their seats, took their places within the enclosure outside the circle, in which stood the casks employed for making the gas. The humbler subscribers, at three francs a-head, occupied the rest of the garden. The number of spectators, as we read underneath the numerous coloured prints which represent this spectacle, was 600,000; but though, without doubt, the gardens of the Tuileries are very large, it is probable this figure is a considerable overstatement, for this number would have been three-fourths of the whole population of Paris. The roofs and windows of the houses were crowded, whilst the Pont Royal and the square of Louis XV. were covered by an immense multitude. About mid-day a rumour was spread to the effect that the king forbade the ascent. Charles ran to the Chief Minister of State, and plainly told him that his life was the king’s, but his honour was his own: his word was pledged to the country and he would ascend. Taking this high ground, the bold professor gained an unwilling permission to carry out his undertaking.