What was the sinister purpose of this gigantic wireless power plant? Only a few men knew, and these often smiled grimly. With feverish haste Chicago's factories were turning out new and strange devices by the thousand--things the purpose of which even their builders did not know. They were tubes of varying sizes, from one foot in length to twelve, made of black enameled steel. The report that the impending battle was very near came sooner than was expected. In the midst of a glorious June day, the sunny serenity of which was mocked by the awful contest that was going on, a lone air scout raced over the city from the south. He brought news that the enemy was preparing every available ship, evidently for the final struggle. Ten minutes after the arrival of the messenger, a hundred and fifty battleships, America's only reserve force, arose majestically from the landing stage to join the main fleet. What appeared to be Chicago's last day of life was drawing to a close when they reached their destination. With this reinforcement the American fleet numbered about 2,000 large battlecraft. They hung stationary, supported high above the earth by their gravitational screens, awaiting the attack. To the south of them, at a distance of perhaps twenty miles, the ships of the enemy were being arranged in battle formation. From deck, port and bridge, keen eyes watched their movements, through powerful glasses. There were at least five thousand of them--all first-class fighting machines of the largest size. Accompanying them was a countless hoard of small fliers. Now the Orientals began to advance in a great V-shaped arrangement. A thousand feet above them, the one-man craft moved like a swarm of hornets. Suddenly the position of the Asiatic fleet seemed to change from south to a little west by south in a way that would have made a man of the twentieth century doubt the evidence of his senses. But these latter-day Americans knew well what was happening. It was merely a weird illusion--another creation of Thomas Whitley's master mind. Soon after he invented the gravitational screen, he had found that, under the influence of certain electromagnetic waves produced by a special generator, air could be made to refract light enormously. This discovery was of tremendous advantage in war. Both the Caucasians and the Mongolians used it to prevent each other from knowing the exact position of their forces. It practically eliminated battles at long range since, without knowing exactly where the enemy is, a gun crew cannot fire with any degree of accuracy. At a range of less than five miles the Whitley "mirafractor," as the device was called, was useless; and consequently within these limits the great contests were fought. At such close quarters the guns shooting projectiles filled with the new radioactive explosive, _terrorium_, could be used with dreadful effect. The Last Stand