complete elements of the disturbing planet, and expressing an opinion, based 

 upon his value of the mass and distance, that it would have a visible disc. 



No. 22. Adams" letter to Prof Airy, Sept. 2, 1846, giving his third solution 

 of the inverse problem of the perturbations of Uranus. This solution (called 

 by him Hypothesis II) gives elements nearer those of Neptune than his former 

 ones, and representing all the normal places, except Flamsteed's, of 1690, 

 satisfactorily. This observation was a barrier to his further approximation 

 towards the reality, being worse represented in his II than in his I Hypothesis. 



No. 23. Letter of Leverrier to Prof Schumacher, Sept. 8, 1846, in which he 

 remarks: 



" Puissent mes recherches inspirer assez de confiance aux astronomes observateurs, pour les 

 engager a s'occuper d'une etude attentive de la partie du ciel, oil il reste sans doute a. decouvrir une 

 planete dont la masse est fort considerable." 



No. 24. Leverrier's unpublished letter to M. Galle, assistant at the Berlin 

 Observatory, Sept. 18, 1846: 



"La nouvelle planete, dont I'existence etait demontree, dont la place etait fixee dans le ciel par 

 les recherches qu'on vient de lire, a ete trouve a Berlin le 23d Septembre dernier. J'avais ecrit le 

 18 Septembre, a M. Galle, pour reclamer son bien velllant concours ; cet habile astronome a vu la 

 planete le jour ou il a re9u ma lettre." 



No. 25. Dr. Galle's receipt of this letter by the post of the 23d, and his 

 setting of the Berlin equatorial in the direction pointed out by Levei'rier, so as 

 to have the planet Neptune in the finder. His actual optical discovery of 

 Neptune as a star not included in Dr. Bremiker's XXI hour of the Berlin star 

 charts. His detection of its motion that evening. His full confirmation of its 

 motion and of the discovery, on the subsequent evening, Sept. 24, 1846. His 

 letter to Leverrier, Sept. 25 : 



"La planete, dont vous avez signale la position, existe reellement. Le meme jour ou j'ai re^u 

 votre lettre, je trouvais une etoile de 8e grandeur, qui n'etait pas inscrite dans I'excellente carte 

 Hora XXI (dessinee par M. le Docteur Bremiker) de la collection des cartes celestes publiee par 

 I'Academie Royale de Berlin. L'observation du jour suivant decide que c'etait la planete cherchee. 



No. 26. Letter of Encke to Prof Schumacher, Sept. 25, 1846, giving the 

 comparison of Leverrier's predicted place with actual observation, as follows: 



Leverrier's prediction, Galle's and Encke'a 

 Aug. 31, 1846. observations. 



V 



375 52 45 



30 54 



73.8 



2.5 



Sept. 23 and 25. — Neptune's heliocentric longitude . . 374 58 



latitude ... 00 



Daily geocentric retrograde motion in longitude 68.7 



Apparent diameter 3.3 



Note to No. 22. — Airy's Account, &c. 



Note to No. 23.— Astr. Nachr., 586. 



Note to No. 24. — Additions a. la connaissance des Temps, 1849. Leverrier's Memoir, dated Paris, October 5, 1846. 



Note to No. 25.— Prof. Schumacher's Circular of September 26, 1846. See also note to No. 24. 



Note to No. 26. — Prof. Schumacher's Circular of September 26, 1846. 



