"The electroscope is an instrument for detecting and testing electrification. A metallic rod passes through the cork of a glass vessel, and terminates on the outside in a ball or a disk. The lower end of the rod carries two strips of gold-leaf or of aluminum foil that hang parallel and close together. When an electrified object is brought near the knob or into contact with it, the metal strips below become similarly charged and are, therefore, mutually repelled." — Avery, 1895

Electroscope

"The electroscope is an instrument for detecting and testing electrification. A metallic rod passes…

"In the gold-leaf electroscope (invented by Bennet in 1787), two light strips of gold-leaf hang from the lower end of a metal rod, which passes vertically through an opening in the top of a glass bottle and expands above into a plate. If a piece of rubbed sealing-wax or other electrified body be brought near the plate, the gold leaves will repel each other and diverge ... A cylinder of wire gauze placed just inside the glass case, improves the action of the instrument." -Hazeltine, 1894

Gold Leaf Electroscope

"In the gold-leaf electroscope (invented by Bennet in 1787), two light strips of gold-leaf hang from…

An illustration of a man repelling down a pole.

Man Repelling Down Pole

An illustration of a man repelling down a pole.

The outline of a bar magnet, and the influence of its poles on a surface covered with iron filings.

Magnetic polse

The outline of a bar magnet, and the influence of its poles on a surface covered with iron filings.