The experiment may be again varied by removing the tube from the liquid, and before lowering it again, allowing 10 or 12 inches of air to enter. This long bubble will be seen to pass slowly down the tube until it arrives at the small opening, when it will be expelled at a great rate. The liquid following this bubble acquires the same velocity, and, arriving at the point, is ejected with such force that it will rise to a height of 6 or 7 feet.
An Electric Fountain
Most of you would like to make an electric fountain, especially when you learn how simple and easily arranged is this striking experiment. Your apparatus consists solely of a glass, a long india-rubber tube, with two small glass tubes and a piece of sealing-wax (a stick of sulphur or piece of vulcanite will do just as well).
Make a small nozzle by drawing out a length of bent glass tubing, and, by means of a long piece of india-rubber piping, fix it to another piece of bent glass tubing. Place the first piece of tubing bent at two right angles over the side of a glass filled with water, taking care that the reservoir thus formed is from 3 to 4 feet above the nozzle ([Fig. 20]).
When the fountain is playing the issuing jet of water will be inclined to one side.
Now to electrify the fountain. Take the piece of sealing-wax, vulcanite, or sulphur, and, after seeing that both your hand and the material you hold are perfectly dry, rub the sealing-wax on the sleeve of your coat.
Fig. 20.—An electric fountain.
If now you hold the sealing-wax opposite the stream of water, at a distance of a few feet, a remarkable change will come over the cascades. Instead of the water falling in scattering drops, these latter will at once unite, and descend in a solid stream, whilst directly the sealing-wax is removed the jet of water returns to its original form. If the water be allowed to fall on a piece of stiff paper, a difference in sound will be noticed according as the water falls in a stream or in drops.