On the 19 October 1875 Sir Charles Wheatstone died

Charles Wheatstone was a British physicist and inventor. In 1834 he used a revolving mirror in an experiment to measure the speed of electricity in a conductor. He the then suggested that the same revolving mirror, could be used to measure the speed of light.

In 1837 Wheatstone and William Cooke patented the 5 needle telegraph (see On This Day 10th June), in 1845 he developed an electric generator in which electricity was induced in coils by an electromagnet initially powered by a battery and then later by the generator itself. In 1854 he invented the Playfair digraph substitution cipher, in 1860 he invented a printing telegraph and 1867 he discovered the principle that the earth’s magnetic field can be used to induce enough magnetism to start an electric generator (this idea was also independently discovered by Cromwell Varley and William von Siemens).

Queen’s Brian May uses Wheatstone technology

In 1929 he invented the concertina, a bellows operated musical instrument, then in 1932 he invented the stereoscope, this is a device that enables two-dimensional drawings or photographs to appear to exist in three dimensions when viewed by both eyes. It is still used today. In September 2020 Brian May, lead guitarist of rock group Queen together with David Eicher launched Cosmic Cloud 3D a ‘visual masterpiece transporting readers into the sublime world of nebulae in stereoscopic (3-D) splendour for the first time’.

The Wheatstone Bridge

In spite of all his own inventions Wheatstone is probably best known for the Wheatstone bridge. This was first invented by British mathematician Samuel Christie but popularised in 1843 by Wheatstone. In its simple form the bridge measures unknown resistance by comparing the current flowing through one part of the bridge with a known current flowing through another part. It can also be used to measure inductance, capacitance, and frequency.