"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.
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