Gas lighting, which dates from 1790, was occasionally used in homes and business premises, mainly by inventors and entrepreneurs. Gas street lighting came into use in Paris in 1820. At that time, the standard way to send messages was to write a letter and send it by horse-drawn carriage; for urgent messages, keep the horse but omit the carriage. The main alternative, mostly restricted to military and official communications, was the optical telegraph. This used semaphore: mechanical devices placed on towers, which could represent letters or words in code by arranging rigid arms at various angles. These configurations could be seen through a telescope and relayed to the next tower in line. The first extensive system of this kind dates from 1792, when the French engineer Claude Chappe built 556 towers to create a 4800 kilometre network across most of France. It remained in use for sixty years. Within a hundred years, homes and streets had electric lighting, electric telegraphy had come and gone, and people could talk to each other by telephone.
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