At noon Captain Restronguet appeared on deck. Kenwyn had just "shot the sun" and was working out the vessel’s position. "It’s about time she was here, Devoran," remarked the captain. "That is, if the report is authentic. Has the submarine detector given no warning?" "No, sir, I’ve stationed Polglaze by it, and he won’t be caught napping. She couldn’t have passed before we arrived, sir?" "I made due allowances, giving her ten knots above her estimated speed. But we must exercise patience. Ah! Mr. Hythe, no doubt you are wondering why we are dodging about here instead of playing harmless little tricks upon His Britannic Majesty’s ships and naval establishments? Well, I think I ought to give you some explanation, so if you will kindly step below we can talk without interruption." "By the by," continued Captain Restronguet, as the two men made their way to the cabin, "you asked me how the ’Aphrodite’ is manoeuvred to bring her to the surface and vice versa. We have three distinct methods. The first is by means of horizontal rudders, there being a pair at both bow and stern; the second is by means of expelling water ballast, which is all very well so long as the ejecting pumps work properly. Hitherto we have had no trouble in this direction, but it is well to be prepared. Consequently we employ a third method--one for use in emergencies only. I make no secret of the fact that I borrowed the idea from the French. I prefer to be original, but at the same time in the interests of my crew I do not hesitate to adopt well-established devices. To each of the three sections of this vessel is fixed a detachable iron keel. The bolts are secured on the keelson by a single yet effective looking device. One thrust of a lever and a section of this keel is dropped. Should a compartment be half full of water there is sufficient buoyancy gained by the release of this dead-weight to lift the vessel to the surface." "Isn’t there a chance of the ’Aphrodite’ buckling her plates in a heavy sea with that dead-weight split into three separate sections?" asked Hythe. "As far as the ’Aphrodite’ is concerned there are no heavy seas," replied his host. "At the first suspicion of bad weather we dive to eight fathoms, or more if necessary. Since, even in mid-Atlantic the waves rarely exceed forty feet in height, and the depth maintained by the submarine is regulated by the vertical height of water over her, there is nothing to be feared as far as the ’hogging’ and ’sagging’ stresses are concerned." At Captain Restronguet’s invitation the sub threw himself into an easy chair. He was eager to hear everything about this mysterious man and his marvellous vessel, and the fact that the Admiralty had given a formal consent for him to remain on board as an official observer relieved him of all anxiety.