No. 27. Leverrier's remark on the receipt of Dr. Galle's letter of Sept. 25, 

 in reply to his of the 18th : 



" Ainsi, la position avait ete prevue a moins d'un degre pres. On trouvera cette erreur bien 

 faible, si I'on reflechit a la petitesse des perturbations dont on avait conclu le lieu de I'astre. Ce 

 succes doit nous laisser esperer qu' apres trente ou quarante annees d'observationsde la nouvelle 

 planete, ou pourra I'employer, a son tour, a la decouverte de celle qui la suit dans I'ordre des distances 

 au soleil. Ainsi de suite; on tombera malheureusement bientot sur des astres invisibles, a cause de 

 leur immense distance au soleil, mais dont les orbites finiront, dans le suite des siecles, par ^tre 

 tracees avec una grande exactitude, au moyen de la theorie des inegalites seculaires." 



No. 28. Letter of ChalUs to Schumacher, Oct. 21, 1846, giving Adams' 

 elements of Neptune from recent observations. 



No. 29. Encke's Memoir read, Oct. 22, 1846, to the Royal Academy of 

 Sciences of Berlin, giv'ng the provisional elements of the planet, and naming it 

 Neptune. Encke remarks: "Neptune's distance from the Sun cannot differ 

 much from 30, while Leverrier's elements give 33. The period must be shorter 

 than Leverrier's. If circular, it would be 165 years." 



No. 30. Detection of Lalande's printed Histoire Celeste observation of 

 Neptune, May 10, 1795, and restoration thereby of fifty-two years to the 

 historical period of our knowledge of the place of this planet, by the author of 

 this Memo ir. 



No. 31. Prof Peirce's communication to the American Academy of Arts and 

 Sciences, March 16, 1847, giving the result of his revision of the theories of 

 Adams and Leverrier, and of my period and present distance in the elements of 

 Feb. 5. Prof Peirce, in this memoir, pronounces the opinion that the theoretical 

 researches of Adams and Leverrier do not comprise the physico-mathematical 

 solution of the problem that belongs to the case of Neptune, and that Dr. Galle's 

 discovery must, therefore, be considered "• a happy accident." 



No. 32. The detection of the Lalande observation of May 10, 1795, by Dr. 

 Petersen, of the Altona Observatory, March 17, 1847. 



No. 33. Leverrier's remark on communicating the Washington and Altona 

 researches relative to the Lalande observation, that — 



" Oette petitesse de I'eccentricite qui semble resulter des calculs de M. Walker serait incompatible 

 avec la nature des perturbations de la planete de Herschel." 



So strong was his conviction of the force of this remark, that he adds: 



" Mais il se pent tres bien que cette petitesse de I'eccentricite ne soit pas une consequence 

 necessaire de la representation de I'observation de Lalande." 



Note to No. 27. — See note to No. 24. 

 Note to No. 28. — Schumacher's Astr. Nachr., No. 583. 

 Note to No. 29. — Schumacher's Astr. Nachr., No. 588. 



Note to No. 30. — See Lieut. Maury's Official Report to the Secretary of the Navy, published February 9, 1846, in the 

 Washington Union. 



Note 1st to No. 31.— See Proceedings of the American Academy of Arts and Sciences, March 18, 1846. 

 Note to No. 32.— Comptes Rendus, March 29, 1847 ; also Astr. Nachr., No. 595. 

 Note to No, 33.— Comptes Rendus, March 29, 1847. 



