he explosion."

"There is no exit, then, from the treasure chamber except along this
corridor?"

"No, madame. The walls at the outside of the chamber are of enormous
strength, because, of course, it was expected that if an attempt at
robbery were ever made, it would be made from the outside, and it is
scarcely possible that even the most expert of thieves could succeed in
passing two guards at the door, sixteen officers and soldiers along the
corridor, two outside the Treasury door, and two in the chamber itself.
Such a large number of soldiers were kept here so that any attempt at
bribery would be impossible. Among such a number one or two were sure
to be incorruptible, and the guards were constantly changed. Seldom was
either officer or man twice on duty here during the month. With such a
large amount at stake every precaution was taken."

"Are there any rooms at the right or left of this corridor in which the
thieves could have concealed themselves while they fired the mine?"

"No, the corridor leads to the treasure chamber alone."

"Then," said Jennie, "I can't see how it was possible for a number of
men to have made away with the treasure in such circumstances as exist
here."

"Nevertheless, my dear young lady, the treasure is gone. We think that
the mine was laid with the connivance of one or more officers on duty
here. You see the amount at stake was so large that a share of it would
tempt any nine human beings out of any ten. Our theory is that the train
was laid, possibly electric wires being used, which would be unnoticed
along the edge of the corridor, and that the bribed officer exploded the
dynamite by bringing the ends of the wires into contact. We think the
explosion was a great deal more severe than was anticipated. Probably,
it was expected that the shock would break a hole from the treasure
chamber to the street, but so strong were the walls that no impression
was made upon them, and a cabman who was driving past at the time heard
nothing of the sound of the explosion, though he felt a trembling of the
ground, and thought for a moment there had been a shock of earthquake."

"You think, then, that the thieves were outside?"

"That seems the only possible opinion to hold."

"The outside doors were locked and bolted, of course?"

"Oh, certainly; but if they had a confederate or two in the large
hallway upstairs, these traitors would see to it that there was no
trouble about getting in. Once ins