Edison patentIn 1912, Thomas A. Edison was issued patents for a “Conveyor” related to a cement kiln, and for a “Phonograph-Stylus” formed of crystallized boron, which because of its hardness (in fact, much harder than sapphire) could operate on sound records formed from hard materials without wearing away. Small crystals of boron could be formed in an electric furnace, and were easier to polish than diamond, while not being as fragile. (U.S. Nos. 1,041,756 and 1,041,983). |