Moreover, to take any further action he would have to see the Observatory librarian. She knew him and his interests too well, and would certainly be intrigued by his request. Probably it would make no difference, but Jan was determined to leave nothing to chance. There would be a better opportunity in a week. He was being super-cautious, he knew, but that added a schoolboy zest to the enterprise. Jan also feared ridicule quite as much as anything that the Overlords might conceivably do to thwart him. If he was embarking on a wild-goose chase, no one else would ever know.

He had a perfectly good reason for going to London; the arrangements had been made weeks ago. Though he way too young and too unqualified to be a delegate, he was one of the three students who had managed to attach themselves to the official party going to the meeting of the International Astronomical Union. The vacancies had been there, and it seemed a pity to waste the opportunity, as he had not visited London since his childhood. He knew that very few of the dozens of papers to be delivered to the I.A.U. would be of the slightest interest to him, even if he could understand them. Like a delegate to any scientific congress, he would attend the lectures that looked promising, and spend the rest of the time talking with fellow enthusiasts, or simply sightseeing.

London had changed enormously in the last fifty years. It now contained scarcely two million people, and a hundred times as many machines. It was no longer a great port, for with every country producing almost all its needs, the entire pattern of world trade had been altered. There were some goods that certain countries still made best, but they went directly by air to their destinations. The trade routes that had once converged on the great harbours, and later on the great airports, had finally dispersed into an intricate web-work covering the whole world with no major nodal points.

Yet some things had not altered. The city was still a centre of administration, of art, of learning. In these matters, none of the continental capitals could rival it — not even Paris, despite many claims to the contrary. A Londoner from a century before could still have found his way around, at least at the city’s centre, with no difficulty. There were new bridges over the Thames, but in the old places. The great, grimy railway stations had gone — banished to the suburbs. But the Houses of Parliament were unchanged; Nelson’s solitary eye still stared down Whitehall; the dome of St. Paul’s still stood above Ludgate Hill, though now there were taller buildings to challenge its preeminence. And the guard still marched in front of Buckingham Palace.

All these things, thought Jan, could wait. It was vacation time, and he was lodged, with his two fellow students, in one of the University hostels. Bloomsbury also had not changed its character in the last century: it was still an island of hotels and boarding-houses, though they no longer jostled each other so closely, or formed such endless, identical rows of soot-coated brick. It was not until the second day of the Congress that Jan got his opportunity. The main papers were being read in the great assembly chamber of the Science Centre, not far from the Concert Hall that had done so much to make London the musical metropolis of the world. Jan wanted to hear the first of the day’s lectures, which, it was rumoured, would completely demolish the current theory of the formation of the planets.

Perhaps it did, but Jan was little the wiser when he left after the interval. He hurried down to the directory, and looked up the rooms he wanted. Some humorous civil servant had put the Royal Astronomical Society on the top floor of the great building, a gesture which the Council members fully appreciated as it gave them a magnificent view across the Thames and over the entire northern part of the city. There seemed to be nobody around, but Jan — clutching his membership card like a passport in case he was challenged — had no difficulty in locating the library.

It took him almost an hour to find what he wanted, and to learn how to handle the great star catalogues with their millions of entries. He was trembling slightly as he neared the end of his quest, and felt glad that there was no one around to see his nervousness.

He put the catalogue back among its fellows, and for a long time sat quite still, staring sightlessly at the wall of volumes before him. Then he slowly walked out into the still corridors, past the secretary’s office (there was somebody there now, busily unpacking parcels of books) and down the stairs. He avoided the elevator, for he wanted to be free and unconfined. There was another lecture he had intended to hear, but that was no longer important now. His thoughts were still in turmoil as he crossed to the embankment wall and let his eye follow the Thames on its unhurried way to the sea. It was hard for anyone with his training in orthodox science to accept the evidence that had now come into his hands. He would never be certain of its truth, yet the probability was overwhelming. As he paced slowly beside the river wall, he marshaled the facts one by one.

Fact one: no one at Rupert’s party could possibly have known that he was going to ask that question. He had not known it himself: it had been a spontaneous reaction to the circumstances. Therefore, no one could have prepared any answer, or had it already lying in their minds.

Fact two: “NGS 549672” probably meant nothing to anyone except an astronomer. Though the great National Geographic Survey had been completed half a century before, its existence was known only to a few thousand specialists. And taking any number from it at random, no one could have said where that particular star lay in the heavens.