The Imps of the Bottle.
Take three little hollow figures of glass, an inch and a half high, representing imps, which may be obtained at a glass-blowers, with a small hole in each of their legs. Submerge them in water in a glass bottle, which should be about fifteen inches high, and covered with a bladder tied over the top. A small quantity of air must be left between the bladder and the surface of the water. When you think fit to command the figures to go down, press your hand hard upon the top, and they will immediately sink; when you would have them rise to the top, take your hand away, and they will float up. By these means, you may make them dance in the middle of the glass at your pleasure.