Le Verrier wrote to Encke, the illustrious director of the Berlin Observatory, desiring him to make a telescopic search for a planetary object situated in the constellation Aquarius, as bright as a star of the eighth magnitude and possessed of a visible disc. “Look where I tell you,” wrote the French astronomer, “and you will see an object such as I describe.” Encke ordered his two assistants, Galle and D’Arrest, to make a search on the night of September 23, 1846. In a few hours Galle observed an object not marked in the star-maps of the Berlin Observatory, which had been recently published. The following night sufficed to show that the object was in motion, and was therefore a new planet. On September 29 Challis found the planet at Cambridge, but he was too late, as the priority of the discovery was now lost to Adams. The planet received the name of “Neptune.” For some time, indeed, it appeared as if the French astronomer alone was to receive the honour of the discovery. But on October 3, 1846, a letter from Sir John Herschel appeared in the ‘Athenæum’ in which he referred to the discovery made by Adams. The French scientists were extremely jealous. Indeed, Arago actually declared that, when Neptune was under discussion, the entire honour should go to Le Verrier, and the name of Adams should not even be mentioned,—Arago’s line of reasoning being that it was not the man who first made a discovery who should receive the credit, but he who first made it public. However, the credit of the discovery is now given equally to Adams and Le Verrier, both of whom are regarded as among the greatest of astronomers. Only a fortnight after the discovery of Neptune, the astronomer Lassell observed a satellite to the distant planet on October 10, 1846. This discovery was confirmed in July 1847 by the discoverer himself, and shortly afterwards by Bond and Otto Struve. Regarding the globe of Neptune, we know practically nothing. No markings of any kind have been observed on its surface. However, in 1883 and 1884, _Maxwell Hall_, an astronomer in Jamaica, noticed certain variations of brilliance which suggested a rotation-period of eight hours, but this was not confirmed by any other astronomer. The spectrum of Neptune has been investigated by various observers, who have found it to be similar to that of Uranus.