Professor Challis thus actually saw the planet twice—­on August 4 and August 12, 1846—­without knowing it.  If he had had a map of the heavens containing telescopic stars down to the tenth magnitude, and if he had compared his observations with this map as they were made, the process would have been easy and the discovery quick.  But he had no such map.  Nevertheless one was in existence.  It had just been completed in that country of enlightened method and industry—­Germany.  Doctor Bremiker had not indeed completed his great work—­a chart of the whole zodiac down to stars of the tenth magnitude—­but portions of it were completed, and the special region where the new planet was expected to appear happened to be among the portions finished.  But in England this was not known.

Meanwhile Adams wrote to the astronomer-royal several additional communications, making improvements in his theory, and giving what he considered nearer and nearer approximations for the place of the planet.  He also now answered quite satisfactorily, but too late, the question about the radius vector sent to him months before.

Leverrier was likewise engaged in improving this theory and in considering how best the optical search could be conducted.  Actuated probably by the knowledge that in such matters as cataloguing and mapping Germany was then, as now, far ahead of all the other nations, he wrote in September (the same year that Sir John Herschel delivered his eloquent address at Southampton) to Berlin.  Leverrier wrote to Doctor Galle, head of the observatory at Berlin, saying to him, clearly and decidedly, that the new planet was now in or close to such and such a position, and that if he would point his telescope to that part of the heavens he would see it; and moreover that he would be able to tell it from a star by its having a sensible magnitude, or disk, instead of being a mere point.

Galle got the letter on September 23, 1846.  That same evening he pointed his telescope to the place Leverrier told him, and saw the planet.  He recognized it first by its appearance.  To his practised eye it did seem to have a small disk, and not quite the same aspect as an ordinary star.  He then consulted Bremiker’s great star-chart, the part just engraved and finished, and, sure enough, no such star was there.  Undoubtedly it was the planet.

The news flashed over Europe at the maximum speed with which news could travel at that date (which was not very fast); and by October 1st Professor Challis and Mr. Adams heard it at Cambridge, and realized that in so far as there was competition in such a matter England was out of the race.