Grace's Guide

British Industrial History

Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 133,998 pages of information and 212,789 images on early companies, their products and the people who designed and built them.

The Engineer 1881/07/01

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Pdf50.jpg 1881 July 01st PDF

Main Subjects

  • Upon a Modification of Wheatstone's Microphone and its Applicability to Radiophonic Researches - By Alexander Graham Bell, p 11.

See Also


Sources of Information