"Not this kind but there have been other kinds." Dr. Pollard looked at the smudge. "Let's take this to Carroll," he suggested. "Maybe it might mean something to that hidden portion of his mind that refuses to admit what it knows about the Lawson Radiation." "Through the teleport?" "Why not? If it's not available at the other end, we'll just meet a solid mirror and can't step through. That worried me for a long time, that idea of not having a place to go to. Just step out into--heaven knows what--because the other end wasn't connected. Come on!" The teleport in Carroll's asylum laboratory gave the physicist warning that they were coming through. He turned as they entered with an annoyed smile on his face. Before him was a long paper record of Lawson Radiation recordings that Carroll was studying through a magnifier. Majors handed Carroll the photo, saying, "What do you make of this?" "It's a bad blur--like a misfocused image," replied Carroll. "Yes--but why?" "You've heard of the Einstein Lens?" "Vaguely, but thought it was just a dream--a probability that never happened." Pollard shook his head. "I don't know about it at all," he admitted. Carroll smiled tolerantly. "Light has energy and energy has mass," he said. "Ergo light has mass. Masses attract one another according to the Newtonian Law of Gravitation. Ergo light is bent by passing close to a mass." "I see," said Pollard leaping to the right conclusion. "Then light radiated from a very distant galaxy may pass close enough to a dark mass--with Terra, the mass and the galaxy in line--to have the distant galaxy focus itself here?" "Yes," replied Carroll. "The mass acts as a biconvex lens because it bends all tangential light toward the center as the beam passes." "But the Einstein Lens effect doesn't make smudges like this," objected Majors. Pollard whistled. "You mean to say that the Einstein Lens is known to be a fact?" "Right. Several cases are known and accepted as such!" "Well!" * * * * * Carroll looked up from the smudge. "A negative lens," he said, "would cause diffusion like this." Majors blinked. "That would mean--oh, no!" "Negative matter," said Carroll promptly. "Um. You postulate a negative mass in line with the light from a star?" Carroll nodded. Majors smiled and took out a roll of thirty-five millimeter film. He handed it to Carroll. "I took the liberty of making smaller prints," he said. "Those are the other thirty-five pix made near that area. You'll see the initiation of the smudge on the second, and the completion of it on the twenty-eighth. The others are just spares." Carroll looked at the smudges, one after the other. "You'll note that the thirteenth, the twentieth, and the twenty-fifth have rather larger areas," said Majors. "Also, on the thirty-first--after the body presumably has passed out of line--there is one more faint flare-point. That was minutes after the thing passed out of line."