File:Detail showing Bell's liquid transmitter in a drawing by P.D. Richards of the experiments in early 1873.jpg

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English: P.D. Richards, Bell's friend and neighbor, wrote the inventor a letter on November 9, 1874 describing the transmission of telegraphic messages over wires using a liquid transmitter filled with mercury. This is a detail of the drawing included with the 1874 letter, which is in the Library of Congress
Source Library of Congress
Author Alexander Graham Bell

35 West Newton Street, Boston, MA


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This work is in the public domain in the United States because it was published (or registered with the U.S. Copyright Office) before January 1, 1923.

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