The apparatus employed for experiments with any kind of air, unless otherwise expressed, consisted of the following parts: 1. A tea-saucer, holding about three ounces of water. 2. A wide-mouthed phial, which would contain about ten ounces of liquid. 3. A small wooden stand, composed of a slender pillar or pin, nearly four inches high, fixed into a round base, a little more than an inch in diameter, and half an inch thick. This stand was fastened by strong thread to the middle of a piece of flat lead, such as lines Chinese tea-chests, having holes in it to admit the thread; the lead was about three inches square, and doubled, to give it weight and stability. The top of the pillar was made pointed; and a round piece of cork, about an inch in diameter and half an inch thick, was fixed upon it, by means of a superficial hole bored in its under part with a gimlet. When the whole apparatus was put in use, the phial was filled with cold pump water, in a pneumatic tub, then inverted, and the species of air to be employed was let up into it, to the quantity of about eight ounces. The subject for experiment being applied to, or fastened upon, the top of the cork, the stand was placed on the tea-saucer, and then introduced, under water, into the phial containing the air. The whole apparatus, being now supported by the tea-saucer, with water in it, was deposited in the laboratory for experiments on light. By this contrivance, the experiments were made in about eight ounces of air, by measure, confined above two ounces of water.