Dated 1843. From Scientific apparatus, musical instruments and telegraph equipment, [1834-1875].

Double cylinder rheostat devised by Wheatstone to maintain a constant current by adjusting or varying the resistance of a circuit.  Consists of two cylinders, one brass and one wood, with wire wound from one cylinder to the other.  A winding handle and brass dial, measuring the number of turns of wire, at the end of the cylinders and mounted on a wooden base.  A description and diagram are in Wheatstone’s papers ref: K/PP107/1/2/64 & 116.  [See also Wheatstone’s Bakerian Lecture for 1843 An account of several new Instruments and Processes for determining the Constants of a Voltaic Circuit published in the Philosophical Transactions of the Royal Society.]