They had come over the mainland of Mexico now and were flying at a height of about half a mile. Shrouded in the tropical twilight, the landscape below was but dimly discernible. As the darkness came on, Ethel discovered that a small light glowed from the side of the car in front of the driver. Gripping the hand-rail, she made bold to raise herself; and, stopping beneath the searchlight and machine-gun that hung, one beneath the other, on swivels in the center of the framework, she peered forward over Komoru's shoulder. The taciturn steersman turned and smiled but said nothing. Ethel noted carefully the equipment of the driver's box. It was a duplicate throughout of the dummy steering gear with which she had practiced in the ship's gymnasium. One conspicuous addition, however, was an object illuminated by the small glow lamp that had attracted her attention. This proved to be chart or map mounted at either end on short rollers. As the girl watched it, she perceived that it moved slowly. A red line was drawn across the map and hovering over this was the tip of a metal pointer. A compass and a watch were mounted at one side of the chart case. Ethel watched the chart creep back on its rollers and reasoned that the pointer indicated the location of the aeroplane. She wondered how the movement of the chart was regulated with that of the plane. Finally she decided to ask Komoru. "By the landmarks and the time," he said. "Do you see that blue coming in on the northeast corner of the map?" "Yes." "Well, watch it." After a few minutes of waiting the words "_Gulf of Mexico_" rolled out upon the chart. "Why, that can't be," said Ethel, "we just left the Pacific Ocean." "But we have crossed the Isthmus of Tehauntepec," replied Komoru; "it is only a hundred miles wide." His companion looked over the side of the car and to the front and. to the right, she could see by the perfectly flat horizon that they were approaching water. "The map is unrolling too fast," said Komoru, as the pointer stood over the edge of the indicated water--and he pushed back the little lever on the clock mechanism that rolled the chart. "We have a little head wind," he added. Ethel resumed her seat and sat musing for a half hour or so. Komoru looked around and called to her. "Look over to your left," he said. "The lights of Vera Cruz. We are making better time now," he added, again adjusting the regulator on the clock work. The driver contemplated his compass carefully and shifted his course a few points to the right. Ethel settled in her bamboo cage and pulled her aviation cap down tightly to shield her face and ears from the wind pressure.