The _Cariad's_ engines were stopped. Captain Parr was seemingly in no hurry to take his ship from that forbidding spot. Nor did he close in order to drop a mark-buoy over the wreckage. A quarter of an hour had passed. The seaplanes, their work accomplished, were out of sight. The light cruiser still lingered. At the microphone apparatus a grave-faced watch-keeping lieutenant was listening, and not listening in vain, for auricular evidences of what was taking place within the as yet water-tight sections of the submersible. Suddenly the muffled roar of a second explosion, of lesser magnitude than that of the first, was borne to the ears of the watchers on the cruiser's deck and superstructure. A thin cloud of vile-smelling smoke filtered through the agitated waves and drifted athwart the _Cariad_. The Deputy Chief of Staff turned inquiringly to Captain Parr. His hands were trembling perceptibly and his tanned features had assumed a greyish hue. "Well?" he inquired laconically. "Done themselves in, poor wretches," replied the owner. "They've detonated the warhead of one of their torpedoes.... Either that or a lingering death." The Captain turned to order speed for fifteen knots. Sir John left the bridge and made his way to the quarter-deck to rejoin his colleagues. "That apparatus of yours, Mr. Strong," he observed in level tones, "is perfectly satisfactory. How many can you guarantee within a fortnight?" He paused and laid his hand upon Brian's masterpiece. "If only you could adapt it for submarine work," he continued, "you would become the greatest humanitarian of the decade--of the century. There would be none of that brutal business we've just witnessed.... Fifty in a fortnight, Mr. Strong? Excellent! Carry on, and let's have the goods." CHAPTER XXVI Orders to Proceed During the next fortnight, Brian Strong kept his augmented staff hard at work. Ninety men were employed in turning out numbers of the apparatus that was to knock the Rioguayan air fleet out of the running. In three shifts the enthusiastic men toiled, Brian personally superintending two shifts a day, while Peter was in charge of the third. Meanwhile the personnel of the Royal Navy was being strongly increased. Ex-officers and men volunteered and were gladly accepted. The fleet reserve was called up, the R.N.R. and R.N.V.R. veterans of the Great War offering their services in shoals. The existing ships, even including those hastily brought forward for commission, were in danger of being over-manned. Owing to the wholesale scrapping of serviceable warships, there were available roughly three times the number of trained men actually required to put every existing ship into commission.