Carruthers nodded. "Time has changed in proportion to our size. We're moving so much faster than the earth that we must of necessity be bound to the universe of which we are now an integral part." For a long time they remained silent, each immersed in dark, troubled thoughts. Nanette broke the silence. "You don't suppose, Aaron, by any chance that Professor Dahlgren is still alive and on our planet?" Carruthers shook his head negatively. "It's beyond human reason, Nan. He was lost in the ray for over forty hours. Translated into minutes he's been gone twenty-four hundred minutes. Since the mouse we placed within the light ray aged approximately two years in the space of one minute, Professor Dahlgren would, if he were alive, be about four thousand, eight hundred years old." Nanette rose abruptly to her feet. "Oh bother the figures. My head's swimming with them. It's getting light now, and I'm hungry." "Eat one of your food tablets," suggested Carruthers. "Please don't get funny," said Nanette. "Karl has them in his coat pocket." "Hum-m-m!" coughed Carruthers, following her example by rising to his feet. "Looks as though we'd have to rustle our food. I've got nothing on my person but a knife, a pencil, a fountain pen and some pieces of paper. Nothing very promising in any of them." * * * * * At that moment the sky became fused with reddish light. Over the horizon appeared a shining orb. Far-away hills and valleys leaped into sight. Then for the first time Carruthers noted the high plateau upon which he had spent the night. Had they ventured a hundred yards farther during the night they would have plunged into the rocky floor of a canyon a thousand feet below. "Let's see if we can find a way down to the valley," he suggested. "If we get anything to eat it will have to come from trees. This plateau is barren of any form of vegetable matter." They found a winding descent leading downward. It looked like a path that had been worn by the passage of many feet. "Someone's been here before us," he exclaimed. "The ground is too well worn to be accidental." "Look! Look!" pointed Nanette. Her face had become pale from the excitement of her discovery. "What is it, Aaron?" Carruthers bent forward to examine the strange footprint. It was nearly two feet across and divided in the center, as if the animal that made it had but two toes. "From the size of the tracks and the length of the animal's stride, I should say it was some form of an amphibious dinosaur long extinct in our own world." "Are they dangerous?" "It all depends upon the species. Some of them are pure vegetarians; others are carnivorous. The heavy tramping we heard during the night evidently came from the beast who left these footprints." * * * * *