"I have my reasons, old man. Do you see the red mud on the rungs of the ladder here?"
"Yes, I see it; but what does that prove?"
"No one has any business in this shaft and yet someone has been here rather recently, for the mud is still soft. That mud came from some one's rubber boots not so many moons ago."
"You ought to be a detective," exclaimed Bob admiringly.
"We will go down now. Be careful. This isn't a very safe place, and a misstep would take you to the surface by the route I followed two weeks ago."
Once on the platform below, the boys halted. Holding their candles above their heads, they looked about them curiously. A new post had been set in place of the old one, the latter still lying on the platform. This the boys examined carefully.
"You see, the post is in good condition, Bob. The post didn't give way, after all. I wonder how it was held up?"
"Perhaps it rested on a piece of wood placed across these two posts that project up through the floor," suggested Bob.
"Yes, that's so. I think you are right. But where is the piece? I should like to see it."
Steve was hunting here and there with his customary energy, while Bob Jarvis stood looking on, not being quite sure what he should do.