"No, not quite," was the reply. "It was built gradually by an enormous number of workers. The tubes are even now extended almost daily to keep pace with the growth of the city." From the stores Ralph took his guests to the roof of an aerocab stand and they boarded a fast flyer. "Take us about 10,000 feet up," Ralph instructed the driver. "You haven't much time," the man answered, "at 12 o'clock all cabs must be out of the air." "Why?" "Today is the 15th of September, the night of the aerial carnival, and it's against the law to go up over New York until it's all over. You have twenty-five minutes left, however, if you wish to go up." "I forgot all about this aerial carnival," said Ralph, "but twenty-five minutes will be time enough for us if you speed up your machine." The aerial flyer rose quickly and silently. The objects below seemed to shrink in size and within three minutes the light became fainter. In ten minutes an altitude of twelve thousand feet had been reached, and as it became too cold, Ralph motioned to the driver not to rise further. The spectacle below them was indescribably beautiful. As far as the eye could see was a broad expanse studded with lights, like a carpet embroidered with diamonds. Thousands of aerial craft, their powerful searchlights sweeping the skies, moved silently through the night, and once in a while an immense transatlantic aerial liner would swish by at a tremendous speed. Most beautiful of all, as well as wonderful, were the _Signalizers_. Ralph pointed them out to his guests, saying: "In the first period of aerial navigation large electric lamps forming figures and letters were placed on housetops, and in open fields that the aerial craft above might better find their destinations. To the traffic flying 5,000 feet or higher such signals were wholly inadequate, as they could not be correctly read at such a distance. Hence the signalizers. These are powerful searchlights of the most advanced type, mounted on special buildings. They are trained skyward and shoot a powerful shaft of light directly upward. No aerial craft is allowed to cross these light shafts. Each shaft gives a different signal; thus the signalizer in Herald Square is first white; in ten seconds it changes to red and in another ten seconds it becomes yellow. Even an aerial liner at sea can recognize the signal and steer directly into the Herald Square pier, without being obliged to hover over the city in search of it. Some signalizers have only one color, flashing from time to time. Others more important use two searchlights at one time, like the one at Sandy Hook. This signalizer has two light shafts, one green and one red; these do not change colors, nor do they light periodically." From on high Ralph's guests marveled at these signalizers, which pierced the darkness all around them. It was a wonderful sight and the weird beauty of the colored shafts thrilled Alice immeasurably.