If a few drops of sulphuric or muriatic acid be let fall into the water, they will gradually stop the motion of the camphor, but if camphor be dropped into nitric acid, diluted with its own bulk of water, it will rotate rapidly for a few seconds and then stop.
If a piece of the rotating camphor be attentively examined with a lens, the currents of the water can be well distinguished, jetting out, chiefly from the corners of the camphor, and bearing it round with irregular force.
The currents, as given out by the camphor, may also be seen by means of the microscope; a drop or two of pure water being placed upon a slip of glass, with a particle of camphor floating upon it. By this means the current may be detected, and it will be seen that they cause the rotations.
A flat watch-glass may be employed, raised a few inches and supported on a wire ring, kept steady by thrusting one end into an upright piece of wood like a retort stand. Then put the camphor and water in the watch-glass, and place under the frame a sheet of white paper, so that it may receive the shadow of the glass, camphor, etc., to be cast by a steady light, placed above, and somewhat on one side of the watch-glass.
On observing the shadow, which may be considered a magnified representation of the object itself, the rotations and currents can be distinguished.
Fire Under Water.
Put thirty grains of phosphorus into a bottle which contains three or four ounces of water. Place the vessel over a lamp and give it a boiling heat. Balls of fire will soon be seen to issue from the water after the manner of an artificial firework, attended with the most beautiful coruscations.