Carroll read the pictures carefully and then without a word he turned to the desk. He picked up the tape of Lawson Radiation recordings and handed it to Majors. "Here," he said, "is correlation between astronomical fact and the Lawson Radiation." There were four definite pips on the line. Four spikes that reached up, with each spike labelled as to the time of reception. Though the intrinsic time did not match by hours the spacing between the pips and the flared photographs was perfect. "Then what?" asked Majors, and Pollard held his breath. "A mass of negative matter passing through space," said Carroll, "would naturally be struck occasionally by meteors or small celestial bodies." "But if negative matter is repulsive instead of attractive?" objected Majors. "Then," said Carroll simply, "the only masses that can strike the repulsive celestial negative-mass are those other masses that possess the velocity that corresponds to the velocity of escape in normal mass!" Majors looked thoughtful. "I get it," said Majors. "The velocity of escape is that velocity attained by any mass in falling to the earth from an infinite distance. Converted, any mass given that velocity upon the instant of departure need have no more acceleration applied in order that the mass be driven to an infinite distance against gravity. Follow?" "Uh-huh," said Pollard. "In the case of a repulsive mass--negative mass--in order for any other object to strike it it must possess enough energy to overcome the repulsion. This would be the inverted equivalent of the velocity of escape!" "Negative mass and positive mass would cancel one another?" Carroll nodded. "Producing the Lawson Radiation!" "Then all these years we have been following a bit of negative mass getting hit by normal meteors." Carroll shook his head. "You check the orbit of that mass," he said, "and you'll find out that it is due to strike Sol!" "You know?" "I suspect," said Carroll. "The aliens must destroy us lest we destroy them. This is their way. We must stop that mass!" "Look," said Majors. "Let's find out the course of that celestial object first!" "It will be," said Carroll. "Carroll," objected Majors, "why must you insist upon blaming the aliens for something that is definitely a matter of celestial chance?" "Because it is not celestial chance," snapped Carroll. "And I'll yet prove it!" CHAPTER XI _Prophets of Doom_ Rita Galloway came at Pollard's request, and the doctor told her about the new developments. She listened with interest, finally nodded with comprehension. "So that," she said, "is what drove him mad?" Pollard smiled. "Obvious, isn't it?" "Not too obvious to one who is not completely informed as to the workings of the mind."