This particular slope was provided with a peculiar arrangement by which a car loaded with slate or other refuse, after being drawn up from the mine to a point a short distance above the surface, could be run backward over a vertical switch that was lowered into place behind it. This vertical switch would carry it out on the dump or refuse heap. The top of the dump presented a broad, level surface for half a mile, on which was laid a system of tracks. Over these the waste cars were drawn by mules to the very edge of the dump, where their contents were tipped out and allowed to slide down the hill-side. During working hours a boy was stationed at this switch, whose business it was to set it according to the instructions received from a gong near him. This could be struck either from the bottom of the mine or the top of the breaker, by means of a strong wire leading in both directions from it. One stroke on the gong meant to set the switch for the mine, and two strokes to set it for the dump. A flight of rude steps led up along the side of the slope from the mouth of the mine to the top of the breaker. Derrick and Paul thought that perhaps they might make their way down this flight of steps and thus escape from the blazing building; but when they reached the end of the slope, and looked down, they saw that this would be impossible. Already the steps were on fire, and the whole slope, as far as they could see, was enveloped in a dense cloud of smoke. Through it shot flaming tongues that were greedily licking the timbers of the tall trestle-work. If Derrick had been alone he would have made the attempt to rush down the steps, and force his way through the barrier of smoke and flame; but he knew that for his companion this would be impossible, and that even to try it meant certain death. As he hesitated, and turned this way and that, uncertain of what to attempt, an ominous crash from behind, followed by another and another, warned them that the floors of the building were giving way and letting the heavy machinery fall into the roaring furnace beneath. They knew that the walls must quickly follow, and that with them they too must be dragged down into the raging flames. Paul, sitting on the floor, buried his face in his hands, shutting his eyes upon the surrounding horrors, and prayed. Derrick stood up, gazing steadily at the rushing flames, and thought with the rapidity of lightning. Suddenly his eye fell upon an empty coal-car standing on the track at the very edge of the slope, and he cried, "Here's a chance, Paul! and it's our only one. Get into this car, quick as you can. Hurry! I feel the walls shaking."