safe-cracking: "Now if the power company's curve is just the same
to-night as last night, that will show how the thing was done. I
wanted to be sure of it, so I thought I'd try this apparatus
which I smuggled in from Paris last year. I believe the old man
happened to be wakeful and heard it."

Then he pried off the door of the interior compartment which had
been jimmied open. "Perhaps we may learn something by looking at
this door and studying the marks left by the jimmy, by means of
this new instrument of mine," he said.

On the library table he fastened an arrangement with two upright
posts supporting a dial which he called a "dynamometer." The
uprights were braced in the back, and the whole thing reminded me
of a miniature guillotine.

"This is my mechanical detective," said Craig proudly. "It was
devised by Bertillon himself, and he personally gave me
permission to copy his own machine. You see, it is devised to
measure pressure. Now let's take an ordinary jimmy and see just
how much pressure it takes to duplicate those marks on this
door."

Craig laid the piece of steel on the dynamometer in the position
it had occupied in the safe, and braced it tightly. Then he took
a jimmy and pressed on it with all his strength. The steel door
was connected with the indicator, and the needle spun around
until it indicated a pressure such as only a strong man could
have exerted. Comparing the marks made in the steel in the
experiment and by the safe-cracker, it was evident that no such