Now the long floor timbers were in place, being supported at the centre by long ropes, hanging from the point of the "A," and the cadets were beginning to lay cross planks on them. "Tell the cavalry to get ready to advance, to protect our crossing," ordered Dutton, to one of his captains, and the troop of lads on their restless steeds prepared to rush across the bridge at the first possible moment. It had only been a little over three minutes since the building of the structure was started, but a heavy artillery fire was being concentrated on the attackers, and, in accordance with instructions previously given, cadets began dropping out, being supposed to be killed. Dutton's field pieces were pounding away, and there was a thick cloud of smoke, which partly concealed the movements of his cadets. "Bridge is ready, major!" reported a smoke-begrimed lad, running up, and saluting. Then he hastened back to continue firing on Hale's soldiers. "Advance, cavalry!" shouted Dutton. "Lively now! Charge!" The horses, urged on by their shouting riders, thundered over the frail bridge. It trembled and swayed, but it supported them. "Forward, the infantry!" cried the young major. "On the double quick! Here they come down the hill at you! Fire at will! Charge!" Down the slope of the hill came rushing the defenders. Behind them thundered and rumbled their artillery, which was supporting their brave advance in the face of the enemy. "Artillery, forward!" shouted Dutton, waving his sword, and hoping, by throwing his entire force suddenly upon Hale's army, to overpower it, and get in more shots than could his opponent. That meant he would win the battle. "Shall I stay here?" cried Dick, for he had received no orders what to do with his force, and was still on the farther side of the bridge. "Yes! Until I send for you, or you see that you are needed," called back Dutton. "I guess I can get along without you." Louder roared the cannon; and the cracks of the rifles of the infantry, and the carbines of the cavalry, was like the explosion of pack after pack of giant firecrackers. Then something happened. As the three field pieces rumbled across the bridge, there was an ominous cracking and splintering sound. Dutton heard it and turned back from his rush, which he had started on to be in readiness to lead the charge of his artillery. He saw the bridge swaying. "Come on! Come on!" he cried, waving his sword. "Come on!" But it was too late. The middle supporting ropes had slipped, and the bridge collapsed at the centre, letting horses, cannon and cadets down into the stream, which, fortunately, was not deep. Dutton had, at one blow, lost all his artillery, while Hale's was advancing to annihilate him and his force. The boom of the defenders' field pieces sounded nearer and nearer, while their rifle fire became hotter than ever.