The vessel was chiefly ballasted with lead fixed to its bottom; when this was not sufficient a quantity was placed within, more or less according to the weight of the operator; its ballast made it so stiff that there was no danger of over-setting. The vessel, with all its appendages and the operator, was of sufficient weight to settle it very low in the water. About 200 lbs. of lead at the bottom for ballast could be let down 40 or 50 feet below the vessel; this enabled the operator to rise instantly to the surface of the water in case of accident. When the operator would descend he placed his foot upon the top of a brass valve, depressing it, by which he opened a large aperture in the bottom of the vessel, through which the water entered at his pleasure; when he had admitted a sufficient quantity he descended very gradually; if he admitted too much he ejected as much as was necessary to obtain an equilibrium by the two brass forcing pumps which were placed at each hand. Whenever the vessel leaked or he would ascend to the surface he also made use of these forcing pumps. When the skilful operator had obtained an equilibrium he could row upward or downward, or continue at any particular depth, with an oar placed near the top of the vessel, formed upon the principle of the screw, the axis of the oar entering the vessel; by turning the oar one way he raised the vessel, by turning it the other way he depressed it. A glass tube 18 inches long and 1 inch in diameter, standing upright, its upper end closed, and its lower end, which was open, screwed into a brass pipe, through which the external water had a passage into the glass tube, served as a water-gauge or barometer. There was a piece of cork with phosphorus on it put into the water-gauge. When the vessel descended the water rose into the water-gauge, condensing the air within, and bearing the cork with its phosphorus on its surface. By the light of the phosphorus the ascent of the water in the gauge was rendered visible, and the depth of the vessel under water ascertained by a graduated line. An oar, formed upon the principle of the screw, was fixed in the forepart of the vessel; its axis entered the vessel, and being turned one way, rowed the vessel forward, but being turned the other way rowed it backward; it was made to be turned by the hand or foot.