Needle telegraph
Carl Friedrich Gauss and Wilhelm Eduard Weber built a telegraph that was used for scientific study and communication between university sites.
Carl August von Steinheil adapted Gauss and Weber's rather cumbersome apparatus for use on various German railways.
In England, William Fothergill Cooke started building telegraphs, initially based on Schilling's design.
On 2 October, André-Marie Ampère, acting on Laplace's suggestion, sent a paper on this idea to the Paris Academy of Sciences.
[3] Johann Schweigger had already invented the galvanometer (in September) using such a multiplier, but Ampère either had not yet got the news, or failed to realise its significance for a telegraph.
Barlow, and other eminent academics of the time who agreed with him, were criticised by some writers for retarding the development of the telegraph.
[5] It was not until 1829 that the idea of applying Schweigger style multipliers to telegraph needles was mooted by Gustav Theodor Fechner in Leipzig.
Fechner, in other respects following the scheme of Ampère, also suggested a pair of wires for each letter (twenty-four in the German alphabet) laid underground to connect Leipzig with Dresden.
Ritchie used twenty-six pairs of wires run across a lecture room as a demonstration of principle.
Schilling's scheme used a bank of six needle instruments which between them displayed a binary code representing a letter of the alphabet.
[10] Transmission speed was very slow on the multi-needle telegraph, perhaps as low as four characters per minute, and even slower on the single-needle version.
The reason for this was principally that Schilling had severely overdamped the movement of the needles by slowing them with a platinum paddle in a cup of mercury.
[11] Schilling's method of mounting the needle by suspending it by a silk thread over the multiplier also had practical difficulties.
[12] In 1833 Carl Friedrich Gauss and Wilhelm Eduard Weber set up an experimental needle telegraph between their laboratory in the University of Göttingen and the university astronomical observatory about a mile and a half away where they were studying the Earth's magnetic field.
[16] The magnet moved so minutely a telescope was required to observe a scale reflected from it by a mirror.
[23] 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.
[24] Cooke was supposed to be studying anatomy, but immediately abandoned this and returned to England to develop telegraphy.
[30] Unsure of how far his telegraph could be made to work, Cooke consulted Michael Faraday and Peter Mark Roget.
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.
[42] 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.
It was made in both single-needle and two-needle forms which in operation were similar to the corresponding Cooke and Wheatstone instruments.
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 detent of the clockwork is released by an electromagnetic armature which operates on the edges of a received telegraph pulse.
