A few days earlier, he had watched the first manned ascent in Montgolfier's hot-air balloon, on. ambassador to France, writing about witnessing, from his carriage outside the garden of Tuileries, Paris, the first manned balloon ascent using hydrogen gas on the afternoon of. Charles, professor of experimental philosophy, and a zealous promoter of that science and one of the Messrs Robert, the very ingenious constructors of the machine. The wind was very little, so that the object though moving to the northward, continued long in view and it was a great while before the admiring people began to disperse. When it was about two hundred feet high, the brave adventurers held out and waved a little white pennant, on both sides of their car, to salute the spectators, who returned loud claps of applause. Between one and two o’clock, all eyes were gratified with seeing it rise majestically from above the trees, and ascend gradually above the buildings, a most beautiful spectacle. Thus it would sooner arrive at that region where it would be in equilibrio with the surrounding air, and by discharging more sand afterwards, it might go higher if desired. Several bags of sand were taken on board before the cord that held it down was cut, and the whole weight being then too much to be lifted, such a quantity was discharged as would permit its rising slowly. Means were used, I am told, to prevent the great balloon's rising so high as might endanger its bursting. Some guns were fired to give notice that the departure of the balloon was near. I then went to the windward side, where they began to form and there the oil, though not more than a tea-spoonful, produced an instant calm over a space several yards square, which spread amazingly, and extended itself gradually till it reached the leeside, making all that quarter of the pond, perhaps half an acre, as smooth as a looking-glass. I saw it spread itself with surprising swiftness upon the surface but the effect of smoothing the waves was not produced for I had applied it first on the leeward side of the pond, where the waves were largest, and the wind drove my oil back upon the shore. At length being at Clapham where there is, on the common, a large pond which, I observed to be one day very rough with the wind, I fetched out a cruet of oil and dropt a little of it on the water.