*The Electrical Dance.* A number of little balls of cork or pith are enclosed in a cylinder of glass about two and one-half or three inches high formed by cutting off the top of a lamp chimney. The top and bottom of the cylinder are closed by two circular pieces of sheet brass or copper. The top disk is connected to the prime conductor while the bottom one is connected to the rubber. When the machine is set in motion, the little balls will dance up and down. Bits of feather or paper cut to represent figures of men and women may be used as well as pith or cork balls. *The Electric Whirl.* The whirl consists of an S shaped piece of brass wire, pointed at both ends and supported on a needle by a little conical depression made in the center with a punch. [Illustration: Fig. 50.—An Electric Whirl.] The needle is stuck in a cork in the top of a bottle and connected with the prime conductor of the electric machine. When the latter is set in motion, the whirl will commence to revolve at a high rate of speed. *Lichtenberg’s Figures* can be produced by charging a Leyden jar by connecting the knob or inside coating with the prime conductor and holding the outside coating in the hand. Then trace a small circle on the electrophorus bed with the knob. Charge a second Leyden jar by connecting the outside coating with the prime conductor. The inside coating should be connected to the rubber by means of a wire fastened to the knob. The same result may be obtained by connecting the outside coating with the prime conductor and touching the knob with the hand. Then trace a cross on the electrophorus bed with the knob, making the cross inside of the circle. [Illustration: Fig. 51.—Lichtenberg’s Figures.] Shake a mixture of red lead and sulphur through a muslin bag from a height of several inches over the electrophorus. The red lead will accumulate around the cross and the sulphur around the circle. CHAPTER IV CELLS AND BATTERIES In order that the young experimenter may obtain electricity for driving his various electrical devices it is necessary to resort to batteries, a small dynamo, or the house-lighting current. All houses are not supplied with electric current. Furthermore, many boys have no source of power from which to drive a small dynamo. Batteries must therefore be resorted to in the majority of cases. A number of different cells and batteries are described in this chapter. All of them are practical, but after buying zinc, chemicals, etc., for any length of time, figure out what your batteries _cost_ you to make. The real value is not their cost in dollars and cents but in what you have _learned_ in making them. If you have a continuous use for electrical current for running _small_ electrical devices it is cheaper to buy dry cells, or what is better, a _storage battery_, and have it _recharged_ when necessary.