Now rub the thick packing-paper over a hot fire or a stove until it is thoroughly dry, and as hot as possible without charring. When this has been done, place it quickly upon a wooden table, and rub it rapidly with as dry and hard a clothes-brush as can be obtained. Place the paper upon the tray; touch the tray with the knuckle, and draw away the paper by the handles fixed to it (see Fig. 2); a spark will result. Then if the paper be replaced upon the tray, and the hand again presented, the same result will follow. This may be done five or six times, at least, with success.
We have in this tea-tray and its paper covering a real electric machine. How can we manage to provide a Leyden-jar (so named from its inventor, Muschenbrock, of Leyden) to contain our electricity? Nothing is more easy. Let us take a tumbler, and partly fill it with shot; insert into the glass a tea-spoon, and if all the articles are quite dry, we shall possess a Leyden-jar.
To charge the jar we must work our other machine. While one person lifts off the paper as directed, another must hold the glass to the edge of the tray, and touch the corner with the tea-spoon; the spark will then enter the "jar." We can thus charge the jar as we please, and by presenting the finger, as in Fig. 3, we shall obtain a discharge from it.
FUN ON THE ICE—"KEEPING THE POT BOILING."
FOOTNOTES:
[1] Begun in No. 101, Harper's Young People.