As Garrick finished his mysterious tinkering and rose from his
dusty job to brush off his clothes, he remarked, "There, now you
may have your heart's desire, Dillon, if all you want to do is to
watch these fellows."

"What is it?" I hastened to ask, looking curiously at the oak box
which contained still everything except the tiny black disc and
the wires leading out of the window from it and from the new
telephone transmitter.

"This little instrument," he answered slowly, "is much more
sensitive, I think, than any mechanical or electrical eavesdropper
that has ever been employed before. It is the detectaphone--a new
unseen listener."

"The detectaphone?" repeated Dillon. "How does it work?"

"Well, for instance," explained Garrick, "that attachment which I
placed on the telephone is much more than a sensitive transmitter
such as you are accustomed to use. It is a form of that black disc
which you saw me hide behind the pile of tires. There are, in
both, innumerable of the minutest globules of carbon which are
floating around, as it were, making it alive at all times to every
sound vibration and extremely sensitive even to the slightest
sound waves. In the case of the detectaphone transmitter, it only
replaces the regular telephone transmitter and its presence will
never be suspected. It operates just as well when the receiver is
hung up as when it is off the hook, as far as the purpose I have
in mind is concerned, as you shall see soon. I have put both forms
in so that even if they find the one back of the tires, even the