Joseph Henry Advises Alexander Graham Bell on Development of Telephone, March - April 1875, Smithsonian Archives - History Div, Alexander Graham Bell visits Secretary Joseph Henry at the Smithsonian to discuss experiments he has conducted involving the telegraphic transmission of vocal sounds. After assuring Bell that he has made an original discovery, Bell agrees to demonstrate the apparatus for Henry. Henry advises Bell to continue his research before publishing his results thus far. In April, Bell writes Henry describing further experimental work on the telephone and his theory of how the apparatus works. Henry responds that he believes this to be original work and that the experiments support Bell's theory regarding the transmission of sound..