The lamp in his cap gave sufficient light for a thorough examination of his prison, and it was soon made. A solid wall of earth and slate surrounded him, the only outlet was through the doors, which were of planks and thickly studded with nails that they might be strong enough to resist a heavy pressure of water.
His only weapon was a stout pocket knife; but even with a saw he could not have cut his way through.
The hinges were next examined. They were fastened to large joists which in turn had been set firmly into the strata of slate.
The only weak point he could find was where the two doors came together, and the flat bolt was exposed. Its entire width and about an inch of its length could be seen thickly covered with rust, and here Sam decided to direct his efforts.
"There isn't much chance I can cut it through in two hours," he said; "but it's better to work than lay still thinking of what may happen."
Breaking the stoutest blade of his knife he began with the jagged surface to scratch at the iron. While cutting through the rust his progress was reasonable rapid; but on firm metal was very much like filing a boiler plate with a pin.
Then the blade of his knife was worn smooth, and he broke off another piece, repeating the operation until the steel had been used to the hilt.
The bolt was cut nearly half through; but as he judged, two hours must have passed.
"If they succeed in flooding the mine I shall still be a prisoner when the water comes," he muttered, and at that moment he heard the sound of approaching footsteps.
Two or more had come from the direction of the shaft, and halted near the door.