"That means that someone in the mine has dropped it from one of the levels."
"Yes, yes."
"Then I would suggest telephoning to the top of the shaft to have the ladder hole leading to the open watched, and no one to be allowed to leave the mine unless able to give a good account of himself."
"Your idea is an excellent one. I will give the order at once."
The superintendent did so; then the men started upward. At Rush's suggestion the party divided. The mine captain had been picked up in the meantime, and the four men divided themselves into two parties, each party taking a level through which it moved, visiting every place where men were at work, questioning each sharply as to whether any of their shift had left their work during the last hour.
The search was fruitless. There were not many men working on the night shift, and beyond considerable ladder climbing, the two parties had finished their search within a few hours.
The four men met on the surface shortly after midnight.
The Iron Boys had nothing to report; neither had Mr. Penton nor the mine captain met with any better results. The mystery was still unexplained.
"Rush, you usually have ideas on most subjects. What do you think about this affair?"