"It'll be a ticklish job, boss."
"I know it, and that's the reason I send the steadiest man in the mine to do it. It's got to be done by somebody, or else it will break through some day and flood the whole lower level."
"All right, sir; I'll do my best wi' it; but I'll be mor'n glad when it's safe done."
With this Tom Evert went on towards the slope; but Derrick stayed behind with the mine boss to learn what he might of the operation of placing the timber supports of a mine roof.
He had not watched this work long when a distant muffled sound, something like that of a blast, and yet plainly not produced by an explosion, reached their ears. Although not loud, it was an ominous, awe-inspiring sound; and Derrick would have taken to his heels and made for the bottom of the slope had not his pride kept him where he was.
To his surprise the mine boss, who had listened intently to the sound while it lasted, seemed to regard it as a most natural occurrence. Giving a few directions to his men, he turned to the boy, saying, "Come, Derrick, let us go and see what is the trouble back in there."
For an instant Derrick looked at him to see if he were really in earnest; then realizing that he was, he followed him without a word.
When they reached Paul Evert's door, the mine boss said, "It's quitting-time, Paul; so get out of this as quickly as you can. It is just possible that we may all have to run," he explained to Derrick, after Paul had obeyed his order and left them, "and in that case all those using crutches will need a good start."
Of course this did not greatly reassure Derrick, and he would gladly have followed his friend Paul had not duty commanded him to remain with his friend the mine boss.
Finally they reached the place where, less than an hour before, Derrick had been helping to "rob" the old heading; and here they discovered the cause of the sound they had heard. The roof above that entire set of workings, so far as they could judge, had fallen; and had not Tom Evert decided to quit work when he did, it is probable that no trace would ever have been found of him or those with him.