“Now some of this light may have to travel a hundred years before it reaches a star. When it does it mixes with other light and is reflected back in another hundred years to us. But—mark you this—but it still carries the image of the earth and what happened on the earth when it was here.” “But you don’t see _that_,” said Tubby. “We see the star. Ain’t I right?” “Yes,” said the professor. “Of course you’re right. And the reason we see the star is because that image is the last one the light got. That is predominate. All the others are there—but they are hidden away beneath the star image.” “Oh,” said Tubby. “Nobody ever knew they were there, and so of course nobody ever tried to get them out. But _I_ knew they were there— that’s the _Oats Theory of the Rationality of Light_. And I have got them out!” His voice rose in triumph. “That’s the Light Machine—the greatest invention in the history of the world!” “Oh, the Light Machine,” said Tubby, when the professor paused. “The Oats Light Machine—here it is—the only one in the world. I’ll show you at once.” He switched off the lights. The room was quite dark except for a little beam of white light that seemed to thread its way through the intricate system of mirrors and prisms of the Light Machine. Tubby could not see where this light came from or where it went to. But he saw distinctly that it turned several corners and was alternately broad and narrow. It was white throughout most of its course; but in one short span it was a dark, angry red, and in another a deep, beautiful purple. “The Light Machine,” the Professor began; his fingers caressed one of its little reflectors lovingly, “is able to extract from light all the images it holds, no matter how long they have been there.” “That’s wonderful, ain’t it?” said Tubby with admiration. “Yes. Let me show you. Here is the telescope. I train it on a star—a star, mark you, that is not a sun, but that shines by reflected light. This beam of starlight, contains moonlight, earthlight, sunlight (_our_ sunlight, you know)—and the light from millions of other suns. The starlight comes out from here”—he touched the lower end of the telescope. “Now you see this ray of my own created light passes directly in front of where the starlight comes out—that’s where they mix.” Tubby saw the little beam of white light crossed at right angles to the telescope eyepiece and passed very close to it. “This light of my own is created by burning zonogen—a gas I discovered myself. “From this point, where the starlight joins it, my ray goes to the spectroscope”—he touched another portion of the Light Machine—“and it is polarized here. These”—he indicated a long row of tiny black compartments; Tubby could see the beam of light entering at one end and emerging at the other—“these are my image extractors. Each takes from the light some of its images—leaving finally only the earthlight and the images that belong to it.