At Christchurch, Marylebone, on February 12, 1847, Wheatstone was married. His wife was the daughter of a Taunton tradesman, and of handsome appearance. She died in 1866, leaving a family of five young children to his care. His domestic life was quiet and uneventful.
One of Wheatstone's most ingenious devices was the 'Polar clock,' exhibited at the meeting of the British Association in 1848. It is based on the fact discovered by Sir David Brewster, that the light of the sky is polarised in a plane at an angle of ninety degrees from the position of the sun. It follows that by discovering that plane of polarisation, and measuring its azimuth with respect to the north, the position of the sun, although beneath the horizon, could be determined, and the apparent solar time obtained. The clock consisted of a spy- glass, having a nichol or double-image prism for an eye-piece, and a thin plate of selenite for an object-glass. When the tube was directed to the North Pole--that is, parallel to the earth's axis--and the prism of the eye-piece turned until no colour was seen, the angle of turning, as shown by an index moving with the prism over a graduated limb, gave the hour of day. The device is of little service in a country where watches are reliable; but it formed part of the equipment of the North Polar expedition commanded by Captain Nares. Wheatstone's remarkable ingenuity was displayed in the invention of cyphers which have never been unravelled, and interpreting cypher manuscripts in the British Museum which had defied the experts. He devised a cryptograph or machine for turning a message into cypher which could only be interpreted by putting the cypher into a corresponding machine adjusted to reproduce it.
The rapid development of the telegraph in Europe may be gathered from the fact that in 1855, the death of the Emperor Nicholas at St. Petersburg, about one o'clock in the afternoon, was announced in the House of Lords a few hours later; and as a striking proof of its further progress, it may be mentioned that the result of the Oaks of 1890 was received in New York fifteen seconds after the horses passed the winning-post.
Wheatstone's next great invention was the automatic transmitter, in which the signals of the message are first punched out on a strip of paper, which is then passed through the sending-key, and controls the signal currents. By substituting a mechanism for the hand in sending the message, he was able to telegraph about 100 words a minute, or five times the ordinary rate. In the Postal Telegraph service this apparatus is employed for sending Press telegrams, and it has recently been so much improved, that messages are now sent from London to Bristol at a speed of 600 words a minute, and even of 400 words a minute between London and Aberdeen. On the night of April 8, 1886, when Mr. Gladstone introduced his Bill for Home Rule in Ireland, no fewer than 1,500,000 words were despatched from the central station at St. Martin's-le-Grand by 100 Wheatstone transmitters. Were Mr. Gladstone himself to speak for a whole week, night and day, and with his usual facility, he could hardly surpass this achievement. The plan of sending messages by a running strip of paper which actuates the key was originally patented by Bain in 1846; but Wheatstone, aided by Mr. Augustus Stroh, an accomplished mechanician, and an able experimenter, was the first to bring the idea into successful operation.
In 1859 Wheatstone was appointed by the Board of Trade to report on the subject of the Atlantic cables, and in 1864 he was one of the experts who advised the Atlantic Telegraph Company on the construction of the successful lines of 1865 and 1866. On February 4, 1867, he published the principle of reaction in the dynamo-electric machine by a paper to the Royal Society; but Mr. C. W. Siemens had communicated the identical discovery ten days earlier, and both papers were read on the same day. It afterwards appeared that Herr Werner Siemens, Mr. Samuel Alfred Varley, and Professor Wheatstone had independently arrived at the principle within a few months of each other. Varley patented it on December 24, 1866; Siemens called attention to it on January 17, 1867; and Wheatstone exhibited it in action at the Royal Society on the above date. But it will be seen from our life of William Siemens that Soren Hjorth, a Danish inventor, had forestalled them.
In 1870 the electric telegraph lines of the United Kingdom, worked by different companies, were transferred to the Post Office, and placed under Government control.
Wheatstone was knighted in 1868, after his completion of the automatic telegraph. He had previously been made a Chevalier of the Legion of Honour. Some thirty-four distinctions and diplomas of home or foreign societies bore witness to his scientific reputation. Since 1836 he had been a Fellow of the Royal Society, and in 1873 he was appointed a Foreign Associate of the French Academy of Sciences. The same year he was awarded the Ampere Medal by the French Society for the Encouragement of National Industry. In 1875 he was created an honorary member of the Institution of Civil Engineers. He was a D.C.L. of Oxford and an LL.D. of Cambridge.
While on a visit to Paris during the autumn of 1875, and engaged in perfecting his receiving instrument for submarine cables, he caught a cold, which produced inflammation of the lungs, an illness from which he died in Paris, on October 19, 1875. A memorial service was held in the Anglican Chapel, Paris, and attended by a deputation of the Academy. His remains were taken to his home in Park Crescent, London, and buried in Kensal Green.