litese sidereal emotion In 365.23 days . . . Akan longitude, October I, 1843 . . . . 323' 34' Longitude of perihelion ......315 33 Excentricbly . . . .... 0•1010 Mani (that of the Sun being unity) . . . 0'0001050 Those elements give 320' 37' for the true heliocentric longitude of the planet on October 1, 1845. The elements of the planet, derived from observations made subsequently to its discovery, assign 324° 48 as its longitude for the same day. The difference therefore between the theoretical and the actual places of the planet amounts to only 49'. The errors in the longitude of Uranus were shown to be accounted for most satisfactorily by the disturbing action of the hypothetic planet.
" Thus it appears that as early as the month of October, 1845, seven months before any other person had arrived at a similar conclusion, Mr. Adams had solved the inverse problem of planetary perturbation ; that by means of his solution he had discovered, theoretically, the existence of a planet exterior to Uranus ; and that he had assigned to the unknown body a place in the heavens which was subsequently found to differ little more than one degree from its actual place. All that was now wanting therefore to assure, both to Mr. Adams and to his country, the undivided honour of one of the noblest discoveries recorded in the annals of science, was some zealous observer to give effect to his results by carefully searching the heavens in the vicinity of the place indicated by his theory as that occupied by the planet. If such a scrutiny had been undertaken, and prosecuted for some time, it would beyond all doubt have resulted in the actual discovery 'of the planet, and the name of Adams would have been alone associated with that remarkable triumph of science. Such a consummation was not destined to be the reward of Mr. Adams ; but this circumstance does not detract in the slightest degree from the merits of his researches; for it is now universally admitted that he was the first theoretical discoverer of the planet, and that as far as the task of the mathematician was concerned he left no part of the problem relative to the determination of its actual position to be completed by others." " Shortly after receiving Mr. Adams's communication respecting the trans-Uranian planet, Mr. Airy wrote to Mr. Adams requesting to know whether the errors in the radius vector of Uranus were accounted for by the action of the undiscovered planet a -9 satisfactorily as the errors in longitude. He considered that the explanation of the errors of the radius vector would form an experimentunt crucis for testing the validity of Mr. Adams's researches, and he has stated that if a satis
factory reply had been returned to his communication he would at once have taken steps to institute a search for the planet.t Mr. Adams inadvertently omitted to furnish Mr. Airy with the desired information. This is more especially to be regretted as it would not have cost him the slightest effort to have returned a satisfactory reply to the Astronomer RoyaL It is right to state that the remarkable researches of Mr. Adams were not hitherto published. In fact it does not appear that at this period any one was acquainted with his labours except a few of his friends at Cambridge and the Astronomer Royal.
Allusion has been made to the failure of Bouvard's attempt to con struct tables of Uranus capable of representing all the observations of the planet. A similar attempt of his nephew, Eugene Bonvard, in 1845, was not attended with much greater success. It was probably this circumstance which induced the late M. Arago, in the same year, to propose to 31. Le Verrier, as a subject of investigation, the irregularities in the motion of Uranus. 31. be Verrier was engaged at the time in researches on the movements of comets, but he did not hesitate to adopt the suggestion of M. Arago, and laying aside his cometary labours for a future occasion, he commenced a rigorous investigation of the theory of Uranus. On the 10th of November, 1845, he communi cated to the Academy of Sciences of Paris an account of the first part of his researches. They consisted in a new determination of the elements of the planet and a careful investigation of the perturbations produced in its motion by all the known bodies of the planetary system which are capable of exercising a sensible influence. On the 1st of June, 1846, M. Le Verrier communicated to the Academy of Sciences an account of the second part of his researches on the theory of Uranus. Finding it impossible to account satisfactorily for all the observations of the planet by the existing theory, he was led to consider whether the outstanding discordances between theory and observation might not be due to the disturbing action of some planet revolving beyond Uranus, and the problem which now presented itself to him was to determine the wherdabouts of the unknown body, corresponding to a given instant of time. The final result which he deduced at this stage of his labours was, that on the 1st of January, 1847, the true heliocentric longitude of the planet was 325°, and that the probable error did not exceed 10°.