"Ah! do not let that trouble you," replied von Schalckenberg. "He cannot break through; he is safely caged, and within the next three hours, please God, we shall all be with you again. Now, please listen, for there is something more that I wish you to do; but this time it is quite easy. You know your way down to the engine-room. Please go down there, taking your telephone with you. When you are there I will tell you what to do." There was a pause of about a minute, and then Lady Olivia again spoke. "Yes, Professor," she said, "here I am. What am I to do?" "How are you standing?" asked von Schalckenberg. "Just inside the engine-room, with my back to the door," came the answer. "Good!" remarked the professor. "Then the machinery is all in front of you. There is a large pipe--as thick as--well, nine inches in diameter at your feet, running across the room from left to right; you cannot mistake it." "Yes," said Lady Olivia. "There is but one of that size near at hand. This one is, as you say, close to my feet." "Now look along that pipe toward your left," directed the professor. "Do you see a small horizontal wheel standing on it, with the spindle running down into the pipe?" "Yes," answered her ladyship. "Then please go to that wheel," said the German. "Grasp it on its right and left with your two hands; pull with your right hand, and push with your left until you cannot turn the wheel any further. Then tell me what happens." A pause of about half a minute ensued, and then Lady Elphinstone spoke again. "I have done as you directed me," she said, "and the engines have stopped!" "Aha!" remarked the professor, with a chuckle of satisfaction. "Yes, that is all right. Now we shall soon overtake you. You need do no more just now, my lady. You can go to your cabin, or where you please. But keep the telephone about you, please, lest we should wish to speak to you again. Courage, madame; you are now quite safe." "Well, Professor, what is the result of your long yarn with Lady Olivia?" demanded Sir Reginald, as he received back his instrument. "Simply that our friend Barker is shut up in the pilot-house, from which he cannot now escape, and Lady Olivia has just cut off the flow of vapour at the generator; in consequence of which the engines have stopped, for one thing, and, for another, Barker may now play as much as he pleases with the levers and valves in the pilot-house without doing any mischief," answered von Schalckenberg. The two boats were by this time off the southern extremity of the reef, with the last oyster of their cargoes gone overboard; they were therefore running light and buoyant over the long swell and sea with which they had to contend, and two minutes later, Mildmay gave the word for them to shift their helms and haul up to their new course of east-north-east. As he did so, he pulled out his watch and noted the time.