1 It is, after all, at least as likely that Rahu - assuming there really was a planet known under this name - might have been Vesta, the brightest of the small planets which circle between Mars and Jupiter, as the distant and slow-moving Uranus. For although Vesta is not nearly so bright as Uranus, shining, indeed, only as a star of the seventh magnitude, yet she can at times be seen without telescopic aid by persons of extremely good sight; and her movements are far more rapid than those of Uranus. In the high table-lands of those eastern countries, where some place the birth of astronomy, keen-sighted observers might quite readily have discovered her planetary nature, whereas the slow movements of Uranus would probably have escaped their notice.

There are three points to be specially noted in this account. First, the astronomer was engaged in a process of systematic survey of the celestial depths-so that the discovery of the new orb cannot be properly regarded as accidental, although Herschel was not at the time on the look-out for as yet unknown planets. Secondly, the instruments he was employing were of his own construction and device, and probably no other in existence in his day would have led him to the discovery that the strange orb was not a fixed star. And thirdly, without the experience he had acquired in the study of the heavens he would not have been able to apply the test which, as we have seen, he found so decisive. The fact that the stars are not magnified by increased telescopic power to the same extent as planets or comets, is, as Professor Pritchard has justly remarked, 'an important result of the undulatory theory of light, and was unsuspected in Sir William Herschel's day.' So that whether we consider the work Herschel was engaged upon, the instruments he used, or the experience he had acquired, we recognise the fact that he alone of the astronomers of his time was capable of discovering Uranus otherwise than by a fortunate accident. Others might have lighted on the discovery-indeed, we shall presently see that the real wonder is that Uranus had not been for many years a recognised member of the solar system - but no one except Herschel could within a few minutes of his first view of the planet have pronounced confidently that the strange orb (whatever it might be) was not a fixed star.

I do not propose to enter here, at length, into the series of researches by which it was finally demonstrated that the newly-discovered body was not a comet but a planet, travelling on a nearly circular path around the sun, at about twice Saturn's distance from that orb. With this part of the work Herschel had very little to do. To use Professor Pritchard's words, having ascertained the apparent size, position, and motion of the stranger, 'Herschel very properly consigned it to the care of those professional astronomers who possessed fixed instruments of precision in properly constituted observatories-to Dr. Maskelyne, for instance, who was then the Astronomer-Royal at Greenwich, and to Lalande, who presided over the observatory in Paris.' As the newly-discovered body travelled onwards upon its apparent path, astronomers gradually acquired the means of determining what its real path might be. At first they were misled by erroneous measures of the stranger's apparent size, which suggested that the supposed comet had in the course of the first month after its discovery approached to within half its original distance. At length, setting aside all these measures, and considering only the movements of the stranger, Professor Saron was led to the belief that it was no comet, hut a member of the solar system. It was eventually proved, chiefly by the labours of Lexell, Lalande, and the great mathematician Laplace, that this theory fully explained all the observed motions of the newly-discovered body, and before long (so complete is the mastery which the Newtonian system gives astronomers over the motions of the heavenly bodies) all the circumstances of the new planet's real motions became very accurately known. It was now possible, not only to predict the future movements of the stranger, but to calculate his motions during former years. This last process was quickly applied to the planet, with the object of determining whether among the records of observations made on stars, any might be detected which related in reality to the newly-discovered body. The result will appear at first sight somewhat surprising. The new planet had actually been observed no less than nineteen times before that night when Herschel first showed that it was not a fixed star, and those observations were made by astronomers no less eminent than Flamstead, Bradley, Mayer, and Lemonnier. Flamstead had seen the planet five several times, each time cataloguing it as a star of the sixth magnitude, so that five such stars had to be dismissed from Flam-stead's lists. But the case of Lemonnier was even more singular; for he had actually observed the planet no less than twelve times, several of his observations having been made within the space of a few weeks. 'M.Arago naturally comments,' says Professor Pritchard, 'on the want of system displayed by Lemonnier in 1769; had he but reduced and arranged his observations in a properly-constructed register, his name instead of

Herschel's would have been attached for all time to one of the starry host. But Lemonnier was not a man of order; his astronomical papers are said to have been a very picture of chaos; and M. Bouvard, to whom we have long been indebted for the best tables of the new planet, narrates that he had seen one of Lemonnier's observations of this very star written on a paper bag which had contained hair powder!'

In our days, when fresh planets are being discovered and named in the course of each year that passes, it may appear strange that much difficulty was found in assigning a suitable name to the stranger. But we must remember that for ages the planetary system had been supposed to comprise no other primary members than those known to the ancients. The discovery of Uranus was an altogether novel and unlooked-for circumstance. It was not supposed that fresh discoveries of like nature would be made, still less that a planet would hereafter be discovered under circumstances far more interesting even than those which attended the discovery of Uranus. Accordingly a mighty work was made before Uranus was fitted with a name. Lalande proposed the name of the discoverer, and the new planet was indeed long known on the Continent by the name of Herschel. The symbol of the planet ( H ), the initial letter of Herschel's name with a small globe attached to the cross-stroke, still reminds us of the honour which Continental astronomers generously proposed to render to their fellow-worker in England.1 Lichtenberg proposed the name of Astraea, the goddess of justice-for this 'exquisite reason,' that since justice had failed to establish her reign upon earth, she might be supposed to have removed herself as far as possible from our unworthy planet. Poinsinet suggested that Cybele would be a suitable name; for since Saturn and Jupiter, to whom the gods owed their origin, had long held their seat in the heavens, it was time to find a place for Cybele, 'the great mother of the gods.' Had the supposed Greek representative of Cybele - Rhaea - been selected for the honour, the name of the planet would have approached somewhat nearly in sound, and perhaps in signification, to the old name Rahu. But neither Astraea nor Cybele were regarded as of sufficient dignity and importance among the ancient deities to supply a name for the new planet.2 Prosperin proposed Neptune as a suitable name, because Saturn would thus have the eldest of his sons on one side of him, and his second son on the other. Bode at length suggested the name of Uranus, the most ancient of the deities; and as Saturn, the father of Jupiter, travels on a wider orbit than Jupiter, so it was judged fitting that an even wider orbit than Saturn's should be adjudged to Jupiter's grandfather. In accepting the name of Uranus for the new planet, astronomers seemed to assert a belief that no planet would be found to travel on a yet wider path; and accordingly when a more distant planet was discovered, the suggestion of Prosperin had to be reconsidered; but it was too late to change the accepted nomenclature, and accordingly the younger brother of Jupiter has had assigned to him a planet circling outside the paths of the planets assigned to their father and grandfather. It may be noted, also, that a more appropriate name for the new planet would have been Coelus, since all the other planets have received the Latin names of the deities.