Visible Speech, the system of expressing speech sounds by written symbols, invented by Prof. Alexander Melville Bell during the years 1849-1864. Its fundamental principle is, says its author, "that all relations of sound are symbolized by relations of form, each organ and each mode of organic action having its appropriate symbol, and all sounds of the same nature produced at different parts of the mouth (such as t and d, b and p) being represented by a single symbol turned in a direction corresponding to the organic position." Among the advantages claimed for visible speech by Professor Bell are its power of representing the exact sounds of foreign languages, and the facilities offered by it toward teaching the illiterate and blind to read, and the deaf and dumb to speak.
Entry from Everybody's Cyclopedia, 1912.