After a long delay a red light swung slowly to and fro on the ledge. From the extreme end of the cañon below the Cat's Paw came the crash of a track-torpedo, answered almost instantly by a second, above the break. It was the warning signal to get into the clear. There was a buzz of rapid movement among the laborers. In twos and threes and dozens, a ragged procession of lanterns and torches, they retreated, foremen urging the laggards, until only a single man at each end of the broken track kept within sight of the tiny red lantern on the ledge. Again it swung in a circle and again the torpedoes replied, this time all clear. The hush of a hundred voices, the silence of the bars and shovels and picks gave back to the chill cañon its loneliness, and the roar of the river rose undisturbed to the brooding night.
On the ledge Glover was alone. The final detail he was taking into his own hands. The few that could still command the point saw the red light moving, and beside it a figure vaguely outlined making its way. When the red light paused, a spark could be seen, a sputtering blaze would run slowly from it, hesitate, flare and die. Another and another of the fuses were touched and passed. With quickening steps tier after tier was covered, until those looking saw the red light flung at last into the air. It circled high between the cañon walls in its flight and dropped like a rocket into the Rat. A muffled report from the lower tier was followed by a heavier and still a heavier one above. A creeping pang shot the heart of the granite, a dreadful awakening was upon it.
From the tier of the upmost holes came at length the terrific burst of the heavy mines. The travail of an awful instant followed, the face of the spur parted from its side, toppled an instant in the confusion of its rending and with an appalling crash fell upon the river below.
With the fragments still tumbling, the nearest men started with a cheer from their concealment. Smoke rolling white and sullen upward obscured the moon, and the cañon air, salt and sick with gases, poured over the high point on which the Pittsburgers stood. Below, torches were shooting like fireflies out of the rock. From every vantage point headlights flashed one after another unhooded on the scene, and the song of the river mingled again with the calling of the foremen.