Applying a higher power, he noticed that it exhibited a planetary disk, but his instrument failed to define it with sufficient distinctness, and hence he became doubtful as to its real nature. The object was found to be in motion, and subsequent observations led him to the assumption that it must be a comet of rather exceptional type. This appeared to be the best explanation of the strange body, for history contained many records of curious comets, some of which were observed as nearly circular patches of nebulous light, and probably of similar aspect to the object then visible; and apart from this it must be remembered that the idea of a large planet exterior to Saturn was a fact of such momentous import that Herschel, with a due regard to that modesty which accompanies true genius, refrained from attaching such an interpretation to his observations. He was content to direct the notice of astronomers to it as a phenomenon requiring close attention, and suggested that it might be a comet in consequence of its motion and the faint and somewhat ill-defined character of its appearance. From the earliest ages five planets only were known, and the discovery of another large planet beyond the sphere of Saturn must at once revolutionize existing ideas as to the range of the solar system, and immediately take rank as a scientific event of equal interest to the discovery of the moons of Jupiter or the rings of Saturn, which each in their day impressed men with new ideas of the celestial mechanism. But the truth could not long be delayed. The new body being watched and its orbit rigorously computed from a series of observed positions revealed its true character, and Herschel was awarded the honor due to the author of a discovery of such importance. His diligence and pertinacity alone had enabled him to search out from among the multitude of stars thickly strewn over the firmament this unknown and well-nigh invisible planet which, during all the preceding years of the world's history, had eluded human perception. Men had been all unconscious of its existence as it had been slowly completing its circuits around the sun, obedient to the same laws as the other planets of the solar system, and awaiting the hour when the unfailing eve of Herschel should introduce it as the faint and far-off planet girding our system within its expansive folds.