ing plate; the uninsulated one, P, the condensing plate. Connect the collecting plate with your electroscope by the wire, W, and bring the condensing plate near it, leaving, however, a thin space of air between them. Charge the collector, P, or the wire, W, with your glass rod, until the leaves of the electroscope begin to diverge. Withdraw the condensing plate, the leaves fly asunder; bring the condensing plate near, the leaves again collapse.
Fig. 27.
Or, vary your construction, and make your condenser thus: Employing the table, or a sheet of foolscap if the table be an insulator, as one plate of the condenser, spread upon it the sheet of India-rubber, P, Fig. 28, and lay upon the rubber the sheet of block-tin, A, B. Connect the tin by the wire, W, with the electroscope, T R L. Impart electricity to the little weight, A, till the leaves, L, begin to diverge; then lift the tin plate by its two silk loops; the leaves, L, at once fly asunder.
Fig. 28.
Finally, show your complete knowledge of the Leyden-jar, and your freedom from the routine of the instrument-makers, by making a "jar," in the following novel way: Stand upon a board supported
