SECTION 1. 



ABSTRACT OF EVENTS CONNECTED WITH THE DISCOVERY OF NEPTUNE, THE PROGRESS MADE 

 IN ITS THEORY, AND THE COMPLETION OF THE THEORY OF URANUS. 



No. 1. The detection of the anomahes of Uranus, and the suggestion of an 

 undiscovered planet as their probable cause, by Alexis Bouvard, in 1821. In 

 his preface, he remarks : 



" Je laisse au temps a venir le soin de faire connaitre, si la difficulte de concilier les deux 

 *systemes tlent i-eellement a I'inexactitude des observations anciennes, ou si elle depend de quelque 

 action etrangere et inapper§ue, qui aurait agit sur la planete." 



No. 2. The correction of certain points in Bouvard's theory of Uranus. The 

 confirmation of the existence of these anomalies. The ascription of them to 

 their true cause, viz., a single transuranian planet, by Bessel, in the years from 

 1821 to 1840. 



No. 3. Bouvard's correspondence with Hansen on the subject of a trans- 

 uranian planet ; the opinion of Hansen that " one body would not satisfy the 

 phenomena ;" and his conjecture " that there were two planets beyond Uranus." 



No. 4. Letter of Rev. T. J. Hussey to Pi'of Airy, Nov. 17, 1834, proposing 

 a search for the transuranian planet. 



No. 5. Answer of Prof Airy, Nov. 21 : " The observations would be well 

 reconciled, if we could from theory bring in two terms : one a small error in 

 Bouvard's eccenti'icity and perihelion, the other a term depending on twice the 

 longitude. The former, of course, we could do ; of the latter, there are two, 

 viz., a term in the equation of the centre, and a term in the perturbations by 

 Saturn. The first I have verified completely, (formula and numbers ;) the second 

 I have verified generally, but not completely. I shall, when I have an oppor- 

 tunity, look at it thoroughly. So much for my doubts as to any extraneous 

 action. But if we were certain that there were any extraneous action, I doubt 

 much the possibility of determining the place of a planet which produced it. I 

 am sure it could not be done till the nature of the irregularity was determined 

 from several successive revolutions." 



Note to No. 1. — The detection of the anomaUes was pubUshed by Bouvard, in the preface to his tables of Uranua, in 

 1891. The date of his iirst suggestion of an undiscovered planet is not stated. 



*Tho orbit with ancient and modern observations, and that from the latter only. 



Note to No. 2. — Bessel's researches on Uranus are contained in the volumes of Schumacher's Astronomische 

 Nachrichten, Nos. 95 and 178. His theory of a transuranian planet is distinctly stated in his lecture to the Physico-eco- 

 nomical Society of Konigsberg, delivered February 23, 1840. 



Note to No. 3. — Since the receipt of Mr. Walker's manuscript. Dr. Gould, in his Report on the History of 

 Neptune, quotes from Hansen a disclaimer of the opinion here attributed to him, having always ascribed the anomalies 

 of Uranus to the action of a single transuranian planet. — Sec- S. I. 



