The growth of the electric telegraph on the railways of Britain

The first practical working installation of an electric telegraph was that brought into service on the Great Western Railway in July 1838. This installation made use of the so-called five needle instrument, which was a development of the four needle version which Cooke had demonstrated to the directors of the London and Birmingham Railway soon after he and Wheatstone had patented their invention in July 1837. The author looks at telegraphy circuits and the part they played in standard timekeeping throughout the country