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by the china cup D, containing 150 grs. of phosphorus; the stopper was then fitted to the opening of the baloon, luted with fat lute, and covered with slips of linen spread with quicklime and white of eggs: When the lute was perfectly dry, the weight of the whole apparatus was determined to within a grain, or a grain and a half. I next exhausted the baloon, by means of an air pump applied to the tube xxx, and then introduced oxygen gas by means of the tube yyy, having a stop cock adapted to it. This kind of experiment is most readily and most exactly performed by means of the hydro-pneumatic machine described by Mr Meusnier and me in the Memoirs of the Academy for 1782, pag. 466. and explained in the latter part of this work, with several important additions and corrections sine made to it my Mr Meusnier. With this instrument we can readily ascertain, in the most exact manner, both the quantity of oxygen gas introduced into the baloon, and the quantity consumed during the course of the experiment.

When all things were properly disposed, I set fire the phosphorus with a burning glass. The combustion was extremely rapid, accompanied with a bright flame, and much heat; as the operation went on, large quantities of white flakes attached themselves to the inner surface of the baloon, so that at last it was rendered