It was evidently the intention of their instructor to prolong their agony, for the flying-boat was still climbing steadily and heading for the Sierra Colima, a range of jagged mountains forming the north-eastern frontier of the republic. Here, there is to be found a perpetual turmoil of air currents, the torrid atmosphere of the plains rising on either side of the mountains and engaging in conflict with the cold blasts of air in the higher regions. Not only were there fierce, eddying winds to be met with, but highly dangerous air-pockets--veritable pitfalls taxing to the uttermost the resources of the pilot. For a good twenty minutes the flying-boat tore madly over the tops of the jagged peaks. Lurching, side-slipping, flung almost vertically through a distance of two hundred feet, twisted like a withered leaf in an autumn gale, the machine provided a series of thrills to the now far from bored Peter. Gripping a metal rod, he divided his attention between the view below, the cool daring of the pilot, and his own efforts to prevent himself being hurled violently against the sides of the fuselage. "That chap is some airman, although he's a Dago," declared Peter. "Those other fellows look like having a very rough time of it." They were. The five were lying utterly helpless upon the floor, sliding in a confused mass every time the machine gave a violent lurch. Greatly to his surprise, Peter felt no sign of air-sickness. Why he was immune he knew not. It was possibly owing to the fact that he was a sailor, but he remembered instances of his late brother officers going up for joy-rides and quickly falling victims to air-sickness. "If I could manage this 'bus," he soliloquized, "and I wanted to clear out of the country, who's there to prevent me? Deal effectively with the pilot and the trick's done. But there's no hurry; there'll be plenty of excitement down there before the time comes to do a bunk with Uncle Brian." Half an hour later, the flying-boat swooped down towards the landing ground. This was a far more exciting bit of work than the comparatively tame ascent. The ground appeared to leap upwards to meet the descending machine. Peter held his breath, fully expecting a terrific bump. The thought flashed through his mind that perhaps the pilot had lost control. Peter watched the custodian of his fate. The pilot was sitting well back in his seat, his right hand grasping the lever controlling the planes. With a slow deliberate movement, he pulled the lever towards him. The flying-boat's speed was instantly checked. Her fore-and-aft axis came to a horizontal position. Then the bows appeared to rise ever so slightly, while at the same moment the four propellers ceased revolving. There was a bump, but it was far less violent than Peter had expected. Another and yet another of less magnitude and the flying-boat was at rest once more on _terra firma_.