"I see, sir," said Jack. "Then the idea is to get as close as possible without being seen, and the moment we are discovered we are to dive?" "Exactly; and if we are so fortunate as to get close enough before being seen, we will launch a torpedo immediately. But we must make the first one count, or we may get the worst of it." Lord Hastings ceased talking and peered intently into the periscope. "Ten minutes more undiscovered," he said, "and we will have him." Five minutes passed, six, seven, and then Lord Hastings gave an expression of deep disgust. "We have been discovered," he said. "Submerge five fathoms." Jack gave the command and the periscope of the D-16 disappeared from view of that of the enemy. "Sheer off to starboard," ordered Lord Hastings. "Should we maneuver aright, we may bring up with her." The D-16 sheered off and dashed forward some distance ere Lord Hastings gave the command to rise that he might take another observation. When the periscope was again above water. Lord Hastings looked quickly around, but could see nothing of the enemy; but even as he looked, the periscope of the enemy's vessel bobbed up less than half a mile away. Quickly Lord Hastings gauged the range and shouted: "Submerge! Quick!" Down went the D-16, and at the same instant Lord Hastings ordered: "No. 4 torpedo!" and giving the range as he had gauged it, commanded: "Ready!" "Fire!" For a moment after the "click" which told that the torpedo had been launched, there was silence. Then Lord Hastings signalled for a rise, that he might ascertain, if possible, whether the shot had gone home. Greatly to his chagrin, he perceived the periscope of the enemy suddenly come up from below. Apparently it had submerged at almost the same instant as had the D-16, and had maneuvered out of harm's way. "Missed her," he informed Jack. At that moment the enemy's submarine dived, and Lord Hastings divined rightly that she was about to launch a torpedo at the D-16. Quickly the course of the D-16 was changed, and she rolled violently as she suddenly turned her nose due south and sped forward. Lord Hastings waited in some anxiety lest his maneuver had not been swift enough. Momentarily he expected to feel a shock that would tell him the Austrian torpedo had struck. But no shock came and Lord Hastings breathed easier. Then he bethought himself of some other plan and consulted Jack, the submarine, meanwhile, remaining far beneath the water. "Other means having failed," said Jack, "I should say, use the searchlight and seek him out." "I guess that is what will have to be done," Lord Hastings agreed. He approached Frank's compartment, and himself took charge of the torpedo there, leaving Jack waiting at the periscope.