Peter had another restless night. He was not altogether satisfied that Uncle Brian's secret would be all that it claimed to be. Unconsciously, he placed himself in the position of Uncle Brian's rival and thought out schemes to counteract the blighting influence of the mysterious rays. Must an aeroplane engine always be fired electrically? he asked himself. Is a magneto or a battery and trembler-coil a _sine qua non_ for the work? It was quite within the bounds of possibility that a dynamo-driven engine might be produced, receiving its current by means of a wireless current. Or there was the hot-bulb engine--far too heavy in its present form for aerial work, but was it too much to expect that in the near future it could be reduced in weight and bulk without any sacrifice of horse-power? "I hope Uncle Brian isn't putting all his eggs into one basket," he soliloquized. "By Jove! I'll try a little experiment on my own account. It will be rough luck on Uncle Brian if it comes off; but better now than later." And with the new-born plan maturing in his active mind, Peter lay awake until pink hues in the eastern sky heralded the dawn of yet another strenuous day. According to his resolve, Brian Strong tackled Jaurez, the chief aviator instructor, on the subject of his nephew's progress. "He is a born bird-man, señor," replied Jaurez, with an admiration that even his secret contempt for Englishmen failed to suppress. "Reckless, _nombre de Dios!_ yes; but he can keep his head. In three days, perhaps, then he will be sufficiently expert to go up in control." "That is good news," said Brian Strong. Suddenly the instructor's mood changed. "For why, Señor Strong, does your nephew wish to fly?" he demanded. "Surely Rioguay can produce sufficient pilots without having to make use of Englishmen?" "I won't dispute that, Señor Jaurez," rejoined Peter's uncle. "But it so happens that there are certain modifications in the design which I wish to test. My knowledge of the Rioguayan tongue is fair, as you know, but there are several technical terms of which I am ignorant. You can readily see that there would be difficulties innumerable if I had to discuss the improvements with a Rioguayan pilot." Señor Jaurez grinned amicably. Previous experience had taught him that Brian Strong's assertion was a correct one. In the earlier stages of the El Toro experimental and constructive works the language difficulty had been a serious obstacle. He was a disciple of the doctrine "follow the line of least resistance". Eight days later, Peter went up for the first time as sole pilot of that notorious flying-boat _El Boyeta_, but on this occasion he was accompanied by three Rioguayan airmen who were sufficiently "salted" to be immune from that distressing malady, air-sickness. Uncle Brian was nowhere to be seen. He had retired to his private experimental shed, having previously given Peter certain instructions.