If the machine is in proper working order a stream of small sparks should flow between the spark balls on the ends of the discharger rods, provided they are not over a half inch apart, when the crank is turned.
The spark can be intensified and lengthened by fitting the machine with two small Leyden jars.
*The Leyden Jars* are made from small test tubes three inches long. The inside of the tube should be coated with tinfoil to within about one inch from the top. The outside of the tube should be coated in the same manner for the same distance. The tinfoil can be secured to the glass with shellac.
The top of the Leyden jars is closed with an ordinary cork. A piece of heavy brass wire bent into the form of a hook should pass through the cork and make connection with the tinfoil on the inside of the tube. One Leyden Jar should be hung over each of the collector rods by means of the hook. The tinfoil coatings on the outside of the jars should be connected together by a piece of wire running across from one tube to the other.
[Illustration: FIG. 12.—Details of the Discharger Rods.]
The machine is now complete and ready for performing a number of very interesting experiments.
Experiments with Static Electrical Apparatus.
*A Leyden Jar* is a very simple device for accumulating and storing static electricity. It consists simply of a wide mouthed jar or bottle coated with tinfoil part way up on both the outside and the inside in exactly the same manner as the small test tubes used on the static machine.
Not all glass jars are suitable for making Leyden Jars. The quality of the glass varies considerably and some will be found far superior to the rest.
The glass vessels used by chemists and called "beaker glasses" usually make excellent Leyden Jars.