His nephew swung himself up by the open entry-port and found himself in the "cargo hold", or what would be in war-time the bombing compartment. From here a door through an armoured bulkhead led to the pilot's "office" immediately above the for'ard pair of engines. "Now, Peter, here they are," announced Brian Strong. "See anything remarkable about these contraptions?" "Sleeveless valves," replied Peter. "Good. Anything else?" "Why, if that's the full tank, it's right over the engine," exclaimed Peter. "And quite a small one at that." "If you'll look, you'll find that there are three tanks to each engine," said his uncle, "and one larger one between each pair of motors. They are gravity tanks fitted with automatic valves, so that whatever position the boat assumes there's always one tank supplying fuel to each motor. Now you see the system of not having the kerosene under pressure until it enters the cylinders. Carburetter--usual type; ignition--magneto." Brian Strong took hold of his nephew's arm, and in a lower voice continued: "That's the heel of Achilles, my boy--the magneto. I've a little gadget I'm perfecting that will knock all existing anti-aircraft devices silly. It will make these flying-boats as harmless as a non-bacteric fly--as a bee without its sting. There'll be no aerial menace, Peter. The blighters who declare that the big battleship is a back number will be utterly confounded. And as for Rioguay----!" He broke off to give a cheerful chuckle. "Let's get back and have breakfast," he said. CHAPTER VII Peter's First Ascent "There is no knowing what tricks these Rioguayans will be up to," observed Uncle Brian, as they gained the open expanse between the workshops and the house. "For instance, I should not be at all surprised if I knew there was a secret dictaphone concealed in each of my private rooms. They are undoubtedly bluffing me--or at least they think they are--and I'm bluffing them in return. So I just carry on, do the work I contracted to do in a thorough and conscientious manner. What I do beyond that is my affair." "I was thinking, Uncle----" "Thinking what?" "Can't you send in a report about what is going on here to the British Government?" "How?" "By letter, or cablegram in code?" "Not an atom of use, Peter. That letter I wrote asking you to join me here was opened by the Rioguayan Government officials. Every scrap of paper that leaves here through the post is carefully examined. They wouldn't accept a code message. It would only serve to increase their suspicions, and that I want to avoid as much as possible. You and I, Peter, are marked men. If, for instance, you went into Tepecicoa, you'd be shadowed from the moment you left till the time you returned." "You said I was to take up flying," persisted his nephew. "What's to prevent me taking you up and making a dash for the West Indies or the Southern States?"