Nevertheless, special training was necessary to overcome the caution against quick turns that long experience had instilled in them all. Each accepted applicant was taken up in one of the new machines, and given a breath-taking ride--a ride that consisted in diving toward the Earth with terrific sudden acceleration. Then, just when the student felt certain they would crash and become a mass of molten metal, the ship was brought up, not a mile from the ground, to settle gently; then, when they almost touched the ground, they leapt into the air again with an acceleration that shot them out of the atmosphere with the velocity of a meteor, while the outer wall of tungsto-iridium alloy glowed cherry red. Then came sharp turns at ten or twenty miles a second, till at last the students no longer gripped the arms of their seats in anticipation of a sudden acceleration. Then they were taken down and given a ship to experiment with. But none of these men had ever handled a weapon of the sort they were to use, so mimic battle practice was held, with the glowing rays of a harmless ionizing beam instead of the deadly Dis rays. * * * * * Daily reports were coming from the Martian scouts as time went on. The Sirians, too, had decided to do some fleet building, for nearly three-quarters of their fleet had been destroyed. The production rate of man's factories, 120,000 a day, had gained a slight lead. It would require ten days before a fleet of a million could leave for Mars with a home guard of two-hundred thousand ships. The destruction of the Martian plants had lowered the production rate to about 3,500 an hour, but shops put up rapidly on Earth and Venus had quickly brought the production-rate back, and it would be nearer 7,000 an hour by the time the last of the fleet had been finished. The spinning sphere formation of the Sirians had been almost invulnerable, and an exceedingly destructive formation. The Solarians had chosen several thousand of their crack pilots to practice this maneuver, but despite almost constant practice during the entire ten days, it was a miserable failure as soon as they tried to progress. Standing motionless it was a very effective procedure, but the spinning column was decided on as more effective as long as they had no ship to protect. There were twenty groups that practiced that maneuver.