THE Scientific American describes a self-resonant tuning-fork, the invention of the indefatigable Edison. It consists of a tube of thick bell-metal closed at one end, and sawed down longitudinally nearly to the closed end, thus making two “prongs” united to a common base. To tune the prongs into unison with the column of air between them, the tube is put into a lathe and turned thinner and thinner until unison is reached. But how such forks are made of any precise pitch, or how the inclosed air-column contrives to vibrate in spite of the long lateral cuts, our contemporary does not vouchsafe to inform us. There are not many organ-pipes that would resound to their proper note with a saw-cut incised down them front and back.