The bar fell to the ground, and the besieged party dashed forth, firing as they emerged. Suddenly, from without, and just as the insurrectos espied the daring sortie, there came the shrill notes of a bugle. At the same instant a ringing cheer came over the top of the stockade. What could it all mean? As if in a dream, the boys saw the insurrectos picking up their rifles and rushing toward the gate. But before they could reach it, a glorious sight greeted them. A regiment of regular Mexican cavalry, the men with their carbines unslung, pouring a disastrous hail into the swarming insurrectos, suddenly swung through the shattered gateway. Shouts and cries responded everywhere within the stockade. The terrified insurrectos dropped their rifles and ran hither and thither in mad, frenzied panic. It was every one for himself. Over the stockade they clambered, many paying toll with their lives before the carbines of Diaz's troopers. But in the midst of the turmoil a clear, boyish voice arose. "Back! Get back, for heaven's sake!" The officer of the Mexican regulars heard, and wheeled his men. He recognized the thrill of warning in Jack Merrill's tones. Stumbling forward, the suddenly relieved party of Americans darted toward the gate for their lives. On down the hillside they fled, with the cavalry surging behind and about them. "What is it? What is the matter?" gasped the officer in English, as Jack stumbled along at his side. The lad gasped out one word: "Dynamite!" Hardly had it fallen from his lips before the ground shook as if convulsed with an earthquake. A red flame shot skyward behind them, and a mighty, reverberating roar went rumbling and echoing over the countryside. The flames had reached the explosive. Almost at the same instant a shower of embers, debris, and odds and ends of all descriptions came showering about the retreating force. Several were cut and bruised by the shower, but none seriously. Fortunately, also, beyond causing several of the cavalry horses to bolt in mad terror, no damage was done to the troops or our friends. The situation was rapidly explained to the wondering officer whose name was Captain Dominguez, in command of the force detailed to guard the railroad. "We learned at Rosario that you had come to the mine," he said, in explanation of the troops' opportune arrival, "and, knowing that Madero was in the habit of raiding mines and was in the neighborhood, we made top speed to the rescue." "And we're all mighty happy to meet you, you kin bet, captain," chimed in Buck, "but ef yer hadn't arrived when you did, we would not have had the pleasure." "No, I can see that," rejoined the young officer, gazing off down the hillside. In every direction could be seen Mexican troopers pursuing rebels, shooting them down, without mercy when fight was shown, in other cases, making prisoners. The rout of the insurrectos was complete and final.