In 1887, having finished the greatest part of his work on the electric light, he turned to the phonograph once more. Realizing that the tin-foil machine was not an ideal type and could not come into common use, he determined to re-design it, and make it an instrument that could be handled by any one.
This meant the design and construction of an entirely different type of machine, and resulted in the kind of phonograph with which every one is familiar in these modern days. One of the chief differences was the use of a wax cylinder instead of tin-foil, and, instead of indenting with a pointed stylus, the record is cut into the wax with a tiny sapphire, the next hardest jewel to a diamond.
Into his improvements of the phonograph Mr. Edison has put an enormous amount of time and work. He has never lost interest, but has worked on it more or less through all the intervening years up to the present time. Even during recent years he has expended a prodigious amount of energy in improving the reproducer and other parts, spending night after night, and frequently all night, at the laboratory.
Inasmuch as great quantities of phonographs were sold, requiring millions of records, one of the difficulties to be overcome was to make large numbers of duplicates from an original record made by a singer, speaker, or band of musicians.
This difficulty will be perceived when it is stated that the record cut into the wax cylinder is hardly ever greater than one-thousandth of an inch deep, which is less than the thickness of a sheet of tissue paper, and in a single phonograph record there are many millions of sound-waves so recorded.
Through endless experiments of Edison and his working force, and with many ingenious inventions, however, these difficulties were overcome one by one.
It may be added that the phonograph was an invention so absolutely new that when Mr. Edison applied for his original patent, in 1877, the Patent Office could not find that any such attempt had ever before been made to record and reproduce speech or other sounds, and the patent was granted immediately. He has since taken out more than one hundred patents on improvements.
The original patent has long since expired, and many kinds of talking-machines are now made by others also, but they all operate on the identical principle which Edison was the first to discover and put into actual practice.