174

HISTORY OF PHYSICAL ASTRONOMY.

the unknown hotly a place in the heavens which was subsequently foundto differ little more than one degree from its actual place. All that wasnow wanting, therefore, to assure both to Mr. Adams and to his countrythe undivided honour of one of the noblest discoveries recorded in theannals of science, was some zealous observer to give effect to hisresults, by carefully searching the heavens in the vicinity of the placeindicated by his theory as that occupied by the planet. If such a scru-tiny had been undertaken, and prosecuted for some time, it would beyondall doubt have resulted in the actual discovery of the planet, and the nameof Adams would have been alone associated with that remarkable triumphof science. Such a consummation was not destined to be the reward ofMr. Adams; but this circumstance does not detract in the slightest de-gree from the merit of his researches ; for it is now universally admittedthat he was the first theoretical discoverer of the planet, and that, as faras the task of the mathematician was concerned, he left no part of theproblem relative to the determination of its actual position to be com-pleted by others.

A few days after the Astronomer Royal received Mr. Adams’ paper con-taining the elements of the new 1 planet, he wrote a letter to that gentleman,thanking him for his communication, and stating that the results appearedto him very satisfactory*. He mentioned, however, that he was desirousof knowing whether the theory gave an equally satisfactory account of theerrors of radius vector, directing Mr. Adams’ attention to the fact of theseerrors having recently become very considerable.

Mr. Airy deemed the explanation of the errors of radius vector to be anexperimentum crucis, which would decide, in his mind, the question of thelegitimacy of Mr. Adams’ researches, and he naturally enough waited forthe reply of that gentleman before taking any active steps for the purposeof discovering the planet. Unfortunately, Mr. Adams did not consider ita matter of importance to transmit prompt information to Mr. Airy onthis point; and it was not until nine months afterwards, when his resultswere confirmed by similar researches, prosecuted in another quarter, thatany attempt was made to obtain their verification. It must not, however,be inferred, from the fact of Mr. Adams not having returned an immediateanswer to Mr. Airy’s letter, that he was prevented from doing so by anyimperfection in his solution of the inverse problem of perturbation. Whenonce the elements of the unknowm planet, and the corrections to the elementsof Uranus , have been deduced from the errors of longitude, the errors ofradius vector may then be calculated by a direct process which does notinvolve any analytical difficulties beyond those already vanquished in theMecanique Celeste . We shall again have occasion to advert to this point.

It is necessary to state, before proceeding further, that Mr. Adams’ re-searches on the theory of Uranus were not hitherto made known to thepublic. The two astronomers whom we have had frequently occasion toallude to in connexion with him, and a few of his friends at Cambridge,appeared to have been the only individuals who were acquainted with thenature of his labours. "We shall now give an account of the researches ofthe French astronomers in connexion with the same subject.

In the month of September, 1845, Eugene Bouvard, nephew of the astro­ nomer Alexis Bouvard , presented to the Institute new tables of Uranus f.They were founded on the observations of the planet made subsequently

* Airy's Hist. Statement, No. 12. This letter is dated the 5th November, 1845.

f Comptes Rendus de l’Academie, tome xxi. p, 524.