He turned and started up the stairway, when the sub-lieutenant, with trembling voice, said: "I am powerless to prevent the explosion,----" "Unless," interrupted the captain. The officer nodded his head. "I supposed so!" continued the captain. "The lieutenant in the galley has the key which controls the automatic device. You may open the door and get the key, and from this time forward, if I find that you deceive me in the slightest degree, or make any attempt to injure the vessel, I will make it your grave without a moment's hesitation, and without the least compunction." The sub-lieutenant moved toward the galley, and opened the door. In a moment he reappeared with the key and followed the captain to the conning tower. Below the switchboard was a tiny slot. Into this the key neatly fitted, and upon giving a turn, a set of switches was exposed. "These are the control circuits," he said. "Turn them off and open the boxes below!" ordered the captain. This was done. "Who are the men that operate the trimming tanks?" asked the captain. "The machinist Scholer and his assistant Bracher," was the reply. "Lieutenant," said the captain, addressing the commander of the chaser; "send those men on board." When they appeared the captain continued: "You will go below with these men, and obey my signals, as we take the vessel to port, and remember, that if any part of the machinery is destroyed I will not guarantee to deliver you safely on shore." As they disappeared, the trap-door was closed, and the boys were free, for the first time since the eventful morning, five days previous to this time, when they stepped aboard the submarine. They now realized, in a particularly pointed manner, that while the air in a submarine seems to be fairly pure, it is filled with the most noxious fumes, due to the petroleum and lubricants, as well as to the odors due to cooking, all of which cannot be gotten rid of, however constantly the air-circulating apparatus of the ship is in operation. The greatest efforts have been made to automatically discharge these odors, but the hundreds of dead corners within a hull of this character make it impossible to effect a thorough discharge, and when the trap-door finally closes down there is a peculiar feeling, not unlike seasickness, which seemed to attack one. "I understand your feelings," said the captain, as he noticed the pale faces of the boys. "It is wonderful how you have been able to keep up, and not exhibit symptoms before this. I will have two seamen come over to assist me in the conning tower." "I wish you wouldn't do that," said Alfred, as he placed his hand on his temples. "I am sure we will get over this in time." "No, no; we want to stay with you, if you don't mind," insisted Ralph. "I am all right now," and he tried to smile, but it was not a very successful effort.