Cooke and Wheatstone telegraph The most widely used needle system, and the first telegraph of any kind used commercially, was the
Cooke and Wheatstone telegraph, employed in Britain and the British Empire in the 19th and early-20th centuries, due to
Charles Wheatstone and
William Fothergill Cooke. The inspiration to build a telegraph came in March 1836 when Cooke saw one of Schilling's needle instruments demonstrated by
Georg Wilhelm Muncke in a lecture in Heidelberg (although he did not realise that the instrument was due to Schilling). Cooke was supposed to be studying anatomy, but immediately abandoned this and returned to England to develop telegraphy. He initially built a three-needle telegraph, but believing that needle telegraphs would always require multiple wires, he moved to mechanical designs. His first effort was a clockwork telegraph alarm, which later went into service with telegraph companies. He then invented a mechanical telegraph based on a musical snuff box. In this device the detent of the clockwork mechanism was released by the
armature of an electromagnet. Cooke carried out this work extremely quickly. The needle telegraph was completed within three weeks, and the mechanical telegraph within six weeks of seeing Muncke's demonstration. Cooke attempted to interest the
Liverpool and Manchester Railway in his mechanical telegraph for use as railway signalling, but it was rejected in favour of a system using steam whistles. Unsure of how far his telegraph could be made to work, Cooke consulted
Michael Faraday and
Peter Mark Roget. They put him in touch with eminent scientist Charles Wheatstone and the two then worked in partnership. Wheatstone suggested using a much improved needle instrument and they then developed a five-needle telegraph. The Cooke and Wheatstone five-needle telegraph was a substantial improvement on the Schilling telegraph. The needle instruments were based on the
galvanometer of
Macedonio Melloni. They were mounted on a vertical board with the needles centrally pivoted. The needles could be directly observed and Schilling's delicate silk threads were entirely done away with. The system required five wires, a slight reduction on that used by Schilling, partly because the Cooke and Wheatstone system did not require a common wire. Instead of Schilling's binary code, current was sent through one wire to one needle's coil and returned via the coil and wire of another. This scheme was similar to that employed by
Samuel Thomas von Sömmerring on his chemical telegraph, but with a much more efficient coding scheme. Sömmerring's code required one wire per
character. Even better, the two needles energised were made to point to a letter of the alphabet. This allowed the apparatus to be used by unskilled operators without the need to learn a code – a key selling point to the railway companies the system was aimed at. Another advantage was that it was much faster at 30 characters per minute. It did not use heavy mercury as the damping fluid, but instead used a vane in air, a much better match for
ideal damping. The five-needle telegraph was first put into service with the
Great Western Railway in 1838. However, it was soon dropped in favour of two-needle and single-needle systems. The cost of multiple wires proved to be a more important factor than the cost of training operators. In 1846, Cooke formed the
Electric Telegraph Company with
John Lewis Ricardo, the first company to offer a telegraph service to the public. They continued to sell needle telegraph systems to railway companies for signalling, but they also slowly built a national network for general use by businesses, the press, and the public. Needle telegraphs were officially superseded by the
Morse telegraph when the UK telegraph industry was nationalised in 1870, but some continued in use well in to the twentieth century.
Other systems The Henley-Foster telegraph was a needle telegraph used by the
British and Irish Magnetic Telegraph Company, the main rival to the Electric Telegraph Company. It was invented in 1848 by
William Thomas Henley and George Foster. It was made in both single-needle and two-needle forms which in operation were similar to the corresponding Cooke and Wheatstone instruments. The unique feature of this telegraph was that it did not require batteries. The telegraph pulses were generated by coils moving through a magnetic field as the operator worked the handles of the machine to send messages. The Henley-Foster instrument was the most sensitive instrument available in the 1850s. It could consequently be operated over a greater distance and worse quality lines than other systems. The
Foy-Breguet telegraph was invented by Alphonse Foy and
Louis-François-Clement Breguet in 1842, and used in France. The instrument display was arranged to mimic the French
optical telegraph system, with the two needles taking on the same positions as the arms of the Chappe semaphore (the optical system widely used in France). This arrangement meant that operators did not need to be retrained when their telegraph lines were upgraded to the electrical telegraph. The Foy-Breguet telegraph is usually described as a needle telegraph, but electrically it is actually a type of armature telegraph. The needles are not moved by a galvanometer arrangement. They are instead moved by a clockwork mechanism that the operator must keep wound up. The detent of the clockwork is released by an electromagnetic armature which operates on the edges of a received telegraph pulse. According to Stuart M. Hallas, needle telegraphs were in use on the
Great Northern Line as late as the 1970s. The
telegraph code used on these instruments was the
Morse code. Instead of the usual dots and dashes of different durations, but the same polarity, needle instruments used pulses of the same duration, but opposite polarities to represent the two code elements. This arrangement was commonly used on needle telegraphs and
submarine telegraph cables in the 19th century after Morse code became the international standard. == Pseudoscience ==