He pressed down on the machine. "There was a pressure here of
considerably over two tons," he remarked at length, "with a very
high horizontal traction of over four hundred pounds. What I
wanted to get at was whether this could have been done by a man,
woman, or child, or perhaps by several persons. In this case, it
was clearly no mere fake to cover up the opening of the door by a
key. It was a genuine attempt. Nor could it have been done by a
woman. No, that is the work of a man, a powerful man, too,
accustomed to the use of the jimmy."

I fancied that a shade of satisfaction crossed the otherwise
impassive face of Langhorne. Was it because the Bertillon
dynamometer appeared at first sight to exonerate Betty Blackwell,
at least so far, from any connection with the crime? It was
difficult to say.

Important though it was, however, to clear up at the start just
what sort of person was connected with the breaking of the door I
could not but feel that Kennedy had some purpose in deferring and
minimizing for the present what, to me at least, was the greater
mystery, the entering of the safe itself.

He was still studying and comparing the marks on the door and the
record made on the dynamometer, when the office telephone rang and
Langhorne was summoned to answer it. Instead of taking the call in
his own office, he chose to answer it at the switchboard, perhaps
because that would allow him to keep an eye also on us.

Whatever his purpose, it likewise enabled us to keep an ear on