d the opening, he procured some fine insulated
wire, and proceeded to make up his circuit: From the arrester, out
beneath the bricks, around the furnace, to the battery; up the wall, and
through the floor by the steam-pipes into the business office; and,
running up-stairs and procuring a step-ladder, on up the office wall,
through the next floor, into the operating room. And there a few minutes
later he had connected the wires to a call-bell on a ledge immediately
behind the table at which he worked. And the alarm was complete.

Although Jack knew that the clerk next door returned from his dinner a
half hour earlier than the others in the express office, he had little
expectation of Smith visiting the cash-box at that time. Nevertheless, as
the noon-hour drew near he found himself watching the alarm-bell with
growing excitement.

"There might be just a chance of Smith visiting the box," he told
himself, "just to learn whether I had--"

From behind him came a sharp "zip, zip," then a whirr. With a bound Jack
was on his feet and rushing for the door. Down the stairs he went, three
steps at a time, and into the manager's private office.

[Illustration: "THERE!" SAID JACK, POINTING IN TRIUMPH.]

"Mr. Black," he cried, "I've got the man who took the box! Down the
cellar! Quick!

"I found the box, with the money still in it, and fixed up an alarm-bell
circuit to go off when he came for it," he explained hurriedly, as the
manager stared. In a moment Mr. Black was on his feet and hastening after
Jack toward the cellar stairway.

Quietly they tiptoed down. They reached the bottom.

"There!" Jack said, pointing in triumph. And looking, the manager beheld
Smith, the express clerk, on his knees beside the furnace, before him on
the floor the missing cash-box.

Ten minutes later the manager of the express company, who had been called
in, passed out of Mr. Black's office with his clerk in charge, and the
telegraph manager, turning to Jack, warmly shook his hand.

"I am more sorry than I can say to have placed the blame upon you, my
boy," he said sincerely. "And I am very thankful for the clever way you
cleared the mystery up.

"You are quite a detective--sort of 'electrical detective'--aren't you?"
he added, smiling.

And for some time, about the office, and even over the wires, Jack went
by that name--the "Electrical Detective."

VI

JACK HAS HIS ADVENTURE

One afternoon a few days following the affair of