He was in the darker shadow of the cañon wall and therefore, of course, quite invisible to whoever was on the river, and who had apparently come to a stop almost opposite to his station. He quickly slipped from his pony, and taking advantage of the brush that grew almost to the water’s edge, he crawled along on his stomach in the direction of the unseen men. At last he gained a position where he could hear them quite distinctly, and could even see their figures bulking up blackly in the general gloom. But what they were doing he could not imagine, and when he finally did find out he received the surprise of his life. Listening to their talk, Jack heard them speaking of Rosario, the leader of the insurgents in that quarter of the Mexican Republic, and apparently they were discussing some mission on which they had been dispatched. He heard the Rangers mentioned, and then came some information that was new to him. The Federal troops of Mexico were hot on the heels of the insurgent army, and the rebels were planning to bring the coming battle on to American soil if possible, in order to force the interference of Uncle Sam. Evidently the men knew of the presence of the Rangers in the locality, and, by listening, Jack soon learned that they were there acting as spies in order to find out how strongly the Border was guarded at that point. Finally they strode off cautiously into the darkness, apparently with the object of reconnoitering the vicinity. This was Jack’s chance. Without a moment’s hesitation he made his way to the river bank and found that a large raft had been moored there. It was evidently on this that the spies had made their way down the stream from some point above. The raft was formed roughly of tree trunks, but appeared to be of stout construction. Some long oars for navigating it lay on the logs; but Jack, in his hasty search, could not see anything on board that might be of interest to Captain Atkinson. He had just completed his examination and was preparing to go back on shore when something happened that changed his plans. As if by magic the figures of the men who had left the raft reappeared at the water’s edge. At the same instant that Jack spied them the men became aware of the intruder on their raft. They did not dare to fire the weapons they carried, owing to the nearness of the Rangers; otherwise they would undoubtedly have done so. Instead, they made a simultaneous leap at Jack, the leader aiming a savage blow at him. The boy dodged the man’s swing, springing backward on the raft. The contrivance had not been securely fastened to the bank. In fact, it had merely been tied carelessly up at the water’s edge. Jack’s sudden spring gave the raft a violent jolt. The current caught it and whirled it round as the strain came upon one side of it. Before either Jack or the Mexicans exactly realized what had occurred, the raft was swept out into midstream, the current hurrying it along swiftly.