Thornton did not reply. He was carefully observing the infinitesimal approach of a certain star to the meridian line, marked by a thread across the circle's aperture. When that point of light should cross the thread it would be midnight, and July 22, 1916, would be gone forever. Every midnight the indicating stars crossed the thread exactly on time, each night a trifle earlier than the night before by a definite and calculable amount, due to the march of the earth around the sun. So they had crossed the lines in every observatory since clocks and telescopes had been invented. Heretofore, no matter what cataclysm of nature had occurred, the star had always crossed the line not a second too soon or a second too late, but exactly on time. It was the one positively predictable thing, foretellable for ten or for ten thousand years by a simple mathematical calculation. It was surer than death or the tax-man. It was absolute. Thornton was a reserved man of few words--impersonal, methodical, serious. He spent many nights there with Evarts, hardly exchanging a phrase with him, and then only on some matter immediately concerned with their work. Evarts could dimly see his long, grave profile bending over his eyepiece, shrouded in the heavy shadows across the table. He felt a great respect, even tenderness, for this taciturn, high-principled, devoted scientist. He had never seen him excited, hardly ever aroused. He was a man of figures, whose only passion seemed to be the "music of the spheres." A long silence followed, during which Thornton seemed to bend more intently than ever over his eyepiece. The hand of the big clock slipped gradually to midnight. "There's something wrong with the clock," said Thornton suddenly, and his voice sounded curiously dry, almost unnatural. "Telephone to the equatorial room for the time." Puzzled by Thornton's manner Evarts did as instructed. "Forty seconds past midnight," came the reply from the equatorial observer. Evarts repeated the answer for Thornton's benefit, looking at their own clock at the same time. It pointed to exactly forty seconds past the hour. He heard Thornton suppress something like an oath. "There's something the matter!" repeated Thornton dumbly. "Aeta isn't within five minutes of crossing. Both clocks can't be wrong!" He pressed a button that connected with the wireless room. "What's the time?" he called sharply through the nickel-plated speaking-tube. "Forty-five seconds past the hour," came the answer. Then: "But I want to see you, sir. There's something queer going on. May I come in?" "Come!" almost shouted Thornton. A moment later the flushed face of Williams, the night operator, appeared in the doorway. "Excuse me, sir," he stammered, "but something fierce must have happened! I thought you ought to know. The Eiffel Tower has been trying to talk to us for over two hours, but I can't get what he's saying." "What's the matter--atmospherics?" snapped Evarts.