“They surely do not intend to assault that hill,” Phil exclaimed; “their loss would be tremendous.” Then he rubbed his eyes, believing that he must have been dreaming. The first line of assault had vanished into the earth. “Why, where did the first line go?” he shouted excitedly, peering down at the remaining columns as they swept silently forward. In but a minute the last enemy had disappeared from sight on the level plain. It seemed like magic. The soldiers whispered nervously to each other. “What can it mean?” Sydney gasped as they gazed in wonder at this remarkable illusion. “Look out,” he cried, as a shrapnel shell exploded over their heads, sending showers of bullets all about them. The artillery fire of the enemy redoubled, and now every gun in the rebel army was concentrating on La Mesa; bursting shell and shrapnel were falling on every hand, and the few defenders of the hill were in momentary danger from their well aimed shooting. “Keep down in the trenches,” the lads warned the excited soldiers. A number had already ventured out to satisfy their curiosity and were stretched in their death agony behind the trench. The midshipmen paced up and down between their guns, apparently unconscious of the death-dealing missiles about them. Their one fear was that the men would break and run before this terrible bombardment was over. Phil braved the storm of iron above his head and took a comprehensive look at the panorama before him. Something unusual was happening on Tortuga Hill; its fire lessened, and down the slope away from the enemy men streamed in countless numbers. Officers could be seen brandishing their swords and gesticulating wildly. Was it a retreat? Phil’s heart rose in his throat. A battery of field guns galloped wildly away down the hill; it reached the level country; the enemy saw its intention and opened upon it a scathing fire. Yet on it came heading directly for La Mesa. The midshipmen cried out for joy and pointed out the nearing aid to their terrorized men. “Steady your men,” Phil urged the lieutenant; “reënforcements are coming.” A cry from Sydney at his side made his hopes sink. “There they come,” he gasped. “We can never stop them.” As Phil took in the situation his blood seemed to freeze in his veins. From the woods in front of La Mesa a swarm of men broke cover and pressed forward on a run. While as if from the ground, midway between them and La Mesa, a seething fire of musketry swept over the handful of defenders. “We have the whole rebel army against us now,” he whispered to Sydney, fearing his men might hear this terrifying intelligence. “It was a trench. They moved in it by the flank and are now in front of us. They must have known this on Tortuga Hill when we saw them hurry our reënforcements to us. If we can hold our men fifteen minutes longer we’ll win.”