Caption:
Thomas A. Edison, U.S. Inventor, Helped Develop World-Wide Industries -- Edison's favorite invention was the phonograph. In 1877 while working with an automatic telegraph, he noticed that the device began to hum musically when it was revolved swiftly. From this Edison perfected a method of recording sound vibrations that could be played back and amplified. Edison, then a young man, is shown with the tinfoil phonograph that he exhibited at the National Academy of Science in Washington. June 20, 1951.