As the general and colonel arrived almost simultaneously, the situation and its necessities became clear. It required but a moment’s investigation by one of the members of the Engineers Corps to verify the fact that the passageway had been effectually blocked by a great wall of earth caved in by the shock of the exploding shell. The general held a short consultation with the colonel of Engineers, and then called both Tom and Harper to them. “Young men,” he said, “we are going to place a great deal of reliance upon your judgment and sense of direction. A straight line drawn from the entrance of this tunnel to the spot where the shell caused a cave-in shows that you were right in saying that it ran almost directly north from where you started. You are sure it takes no turns?” “Not until the very entrance to the bomb chamber,” Tom answered quickly; and Harper corroborated him. “Very well,” the commander went on quickly. “If that is true, then we are saved some unnecessary labor. It is not likely that we could dig directly into the tunnel from any given spot, but we will proceed directly northward to a point which you consider near to the chamber, but yet a safe distance away, then try to effect an entrance.” And with competent engineers directing a true northward course, they proceeded rapidly toward Thiaucourt. Tom, who had been considering the distance carefully, came to a halt and saluted. “I would suggest, sir, that perhaps this is as near as is safe to begin the digging.” “Very well,” the general replied, and nodded to the colonel. A moment later fifty men with spades were lined up before their commander for instructions. He marked the spot where the tunnel might be, and then, at right angles to the direction they had walked, or almost directly east and west, he established an imaginary line. “Dig along that, working toward this point at the centre,” he ordered. “Somewhere along that line you should strike the tunnel. Proceed with care after you are six or seven feet deep.” Every man there had a fair idea of what depended upon cutting the connection to those bombs before, somewhere to the north, a German hand reached for a switchboard and turned on the current that would cause a holocaust. Also, they knew that they were about the closest in proximity to those hidden mines, so there was no lack of incentive for all the speed that strength could muster. Dirt flew out of that ever deepening and lengthening pit in a constant cloud, piling up a high trench work on either side. But despite the care to which they had cautioned, it was the muffled exclamation of surprise from a man suddenly dropped downward with a great accompanying scraping and crashing of earth, that heralded the discovery of the tunnel.