"How does it work?" I asked, much mystified.
"Well, it is based on an entirely new principle, in every way different from the phonograph," he explained. "As you can see there are no discs or cylinders, but these spools of extremely fine steel wire. The record is not made mechanically on a cylinder, but electromagnetically on this wire."
"How?" I asked, almost incredulously.
"To put it briefly," he went on, "small portions of magnetism, as it were, are imparted to fractions of the steel wire as it passes between two carbon electric magnets. Each impression represents a sound wave. There is no apparent difference in the wire, yet each particle of steel undergoes an electromagnetic transformation by which the sound is indelibly imprinted on it."
"Then you scrape the wire, just as you shave records to use it over again?" I suggested.
"No," he replied. "You pass a magnet over it and the magnet automatically erases the record. Rust has no effect. The record lasts as long as steel lasts."
Craig continued to tinker tantalizingly with the machine which had been invented by a Dane, Valdemar Poulsen.
He had scarcely finished testing out the telegraphone, when the laboratory door opened and a clean-cut young man entered.
Kennedy, I knew, had found that the routine work of the Clutching Hand case was beyond his limited time and had retained this young man, Raymond Chase, to attend to that.
Chase was a young detective whom Craig had employed on shadowing jobs and as a stool pigeon on other cases, and we had all the confidence in the world in him.