page_title: Needle telegraph
section_title: Early ideas
hierarchical_section_title: Needle telegraph / Early ideas
caption_attribution_description: Deutsch: Schweigger Multiplikator
context_page_description: A needle telegraph is an electrical telegraph that uses indicating needles moved electromagnetically as its means of displaying messages. It is one of the two main types of electromagnetic telegraph, the other being the armature system as exemplified by the telegraph of Samuel Morse in the United States. Needle telegraphs were widely used in Europe and the British Empire during the nineteenth century.
  Needle telegraphs were suggested shortly after Hans Christian Ørsted discovered that electric currents could deflect compass needles in 1820. Pavel Schilling developed a telegraph using needles suspended by threads. This was intended for installation in Russia for government use, but Schilling died in 1837 before it could be implemented. 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. With Charles Wheatstone, Cooke produced a much improved design.
context_section_description: The history of the needle telegraph began with the landmark discovery, published by Hans Christian Ørsted on 21 April 1820, that an electric current deflected the needle of a nearby compass.  Almost immediately, other scholars realised the potential this phenomenon had for building an electric telegraph.  The first to suggest this was French mathematician Pierre-Simon Laplace.  On 2 October, André-Marie Ampère, acting on Laplace's suggestion, sent a paper on this idea to the Paris Academy of Sciences.  Ampère's (theoretical) telegraph had a pair of wires for each letter of the alphabet with a keyboard to control which pair was connected to a battery.  At the receiving end, Ampère placed small magnets (needles) under the wires.  The effect on the magnet in Ampère's scheme would have been very weak because he did not form the wire into a coil around the needle to multiply the magnetic effect of the current.  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.
  Peter Barlow investigated Ampère's idea, but thought it would not work.  In 1824 he published his results, saying that the effect on the compass was seriously diminished "with only 200 feet of wire".  Barlow, and other eminent academics of the time who agreed with him, were criticised by some writers for retarding the development of the telegraph.  A decade passed between Ampère's paper being read and the first electromagnetic telegraphs being built.
caption: Schweigger multiplier
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