On board the submarine the lads were enjoying themselves as much as their fellow Scouts on the motor boat. This second experience was even more novel and enjoyable than their first dive. Mr. Barr sat in the cabin reading some scientific works. Barton, seemingly a changed character, was at work in the engine room. The negro cook was in the galley, while in the conning tower the ensign was giving Donald and Merritt a lesson in handling a diving craft. In fact, it was Merritt who was at the deflecting apparatus when the occupants of Tubby's boat saw the submarine sink. "That is the descending lever and this the ascending one," explained the officer before Merritt sent the boat under the surface. The levers were small affairs and looked fragile for the work they did of starting up the mighty pumps that caused the boat to rise or sink at will. "What if one of them should break or be lost?" asked Donald. "Well, if we were under water and the ascending lever happened to be missing, we should be in an awkward position, and I don't believe that Mr. Barr carries an extra one." "Gracious! Then if the lever was lost we should have to stay at the bottom of the sea?" "That's about the size of it," was the reply. Mr. Barr, coming into the conning tower just then, confirmed the officer's suspicion that no extra lever was carried. "I admit there ought to be one as a matter of precaution," he said, "but we were in such a hurry to give the boat her tests that we forgot about it." All the afternoon the submarine ran under the water, rising about sunset to the surface. In the distance was the motor boat, but far in the rear. The _Peacemaker_ was sent around in circle and soon came alongside her companion craft. Then the hatchway was opened and the ensign shouted some orders to Tubby. The submarine was going to dive once more, but would come up before dark. When night fell a red light would be carried astern which the motor craft was to follow throughout the night. When this had been made clear, the _Peacemaker_ dived once more, but this time it had been decided to send her down to a good depth. "We will eat an early supper under water just for the novelty of it," declared Mr. Barr. While the meal was going forward Barton was sent into the conning tower to navigate the craft. He obeyed with the same smooth complacence with which he had received every order since his attack on Donald. Evidently the man was hoping, by good behavior, to save himself from a long jail sentence. After supper Barton was relieved, and Merritt sent to the wheel in his place. He had been in the conning tower but a short time when he was joined by Ensign Hargreaves and Mr. Barr. "I guess we'll go to the surface now," said the inventor; "it must be almost dark up above." Merritt reached for the lever that operated the ascending pumps. Right then he received the most acute and alarming shock of his life. There was no lever there! "It's gone!" he shouted.