Harris's Balance Electrometer, 1834.

Harris's balance electrometer, 1834.

Henley's electrometer, c 1770.

Experimental model of induction balance Pr

Quadrant electrometer built by Pierre Curie, 1880s.

Quadrant electrometer built by Pierre Curie, 1880-1890.

Balance with marble top, 19th century.

Celtic bronze balance beam and lead weight, Isle of Man, 8th century.

Spanish balance beam, Seville, 17th century.

Cord pivot, balance and set of weights, ivory, Persian, 16th century.

Prehistoric Egyptian balance beam, c 5000 BC.

Automatic pan balance, 1964.