This book deals with the works of Graham Bell and other scientists on the phenomena of sound and its production. “In bringing before you some discoveries made by Mr. Sumner Tainter and myself, which, having resulted in the construction of apparatus for the production and reproduction of sound by means of light, it is necessary to explain the state of knowledge which formed the starting-point of our experiments. I shall first describe the remarkable substance selenium, and the manipulations devised by various experimenters; but the final result of our researches has extended the class of substances sensitive to light-vibrations, until we can propound the fact of such sensitiveness being a general property of all matter.” ABOUT THE AUTHOR Alexander Graham Bell (1847–1922) was a Scottish-born inventor, scientist, teacher of the deaf, and innovator who is best known for inventing the telephone.