In the midst of the battle, the Solarians began to wonder why the Nigran fleet was decreasing so rapidly--certainly they had not caused all that damage! Then suddenly they found the answer. One of their ships--then another--and another fell victim to a pale red ray that showed up like a ghostly pillar of luminosity coming from nowhere and going nowhere! The answer? The invaders' ships were becoming invisible! The invisibility detectors were being overloaded now, and the hunt was hard, while the Nigrans were slipping past them and silently destroying Solarian ships! The molecular motion rays were quite effective on an invisible ship--once it had been found. They were destroying the Nigrans as rapidly as they were being destroyed, but they were letting some of them slip past! The luminous paint bombs and bullets were now called into play. All enemy ships were shot at with these missiles, and invisibility was forestalled. At long last the dark bulk of the main fleet approached, a scarcely visible cloud of tiny darting metal ships. The battle so far had been a preliminary engagement. The huge ships of the Nigrans were forced to stop their attack, and releasing the last of the fliers, to retire to a distance, protected by a screen of small ships, for they were helpless against the Solarian speedsters. Invisibility fell into disfavor, too, now that there were plenty of Solarian ships, for the Nigrans were more conspicuous when invisible than when visible. The radio detector could pick them out at once. The entire Nigran fleet was beginning to reveal the disorder and uncertainty that arose from desperation, for they were cornered in the most undesirable position possible. They were outside the Solarian fleet, and their ships were lighted by the glare of the sun. The defenders, on the other hand, were in such a position that the enemy could see only the "night" side of them--the shadowed side--and, as there was no air to diffuse the light, they were exceedingly hard to find. In the bargain, the radium paint was making life for the Nigrans a brief and flitting thing! The invaders began to pay an awful toll in this their first real engagement. They lacked the necessary power to cover the entire Solarian fleet with their death rays, and their heat weapons were of little help. The power of the small ships did not count for much--and the big liners could not use their weapons effectively for their small fliers must be between them and their adversary. Despite this, however, the Nigrans so greatly outnumbered the Earth-Venus forces that it looked as though a long and costly war lay ahead.