HISTORY OF PHYSICAL ASTRONOMY.

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obvious that they could not be treated with indifference. Under suchcircumstances the course obviously suggested by a due regard to the sacredclaims of right and the dignity of science, would have been to suspendjudgment on the question altogether, pending the publication of Mr.Adams’ researches which were announced as speedily forthcoming. M.Arago, actuated, beyond doubt, by a laudable desire to defend the rights ofhis countryman from what he conceived to be an unjustifiable aggression,took a different view of the matter, and at once undertook a criticalexamination of the merits of Mr. Adams in regard to the theoreticaldiscovery of the Trans-Uranian planet. The paper which he drew up onthis occasion is inserted in the Comptes Rendus for the 19th October,1840 *. We shall not here make any allusion to the assumptions which M.Arago so unwarrantably employs in the absence of acknowledged facts,with the view of preserving the consistency of his reasoning. Theirfallacy was effectually exposed a few weeks afterwards, without any contro-versy, by the publication of the admirable researches of Mr. Adams, and ofthe important mass of documentary correspondence in the possession ofMr. Airy, relative to the discovery of the planet. We shall merelymake a few remarks on the main principle laid down by him, and theconclusion which he seeks to draw from it. He assumes, as the basis

* This paper contains a view of certain communications of Professor Challis whichtends at first appearance to lead to a conclusion totally inconsistent with the real state-ments of the English astronomer. M. Arago asserts that Professor Challis, writing to himon the subject of the planet, uses the following words:—“ I became acquainted on the 29thSeptember with the final researches of M. Le Verrier; I conformed strictly to the sug-gestions of that astronomer, and confined my search within the limits assigned by him.”ile then remarks that Professor Challis in his letter to the Athenaeum , announcesthat he was guided in his search for the planet by a paper which Mr. Adams drewup for him. Having placed these two apparently contradictory statements in juxta-position, M. Arago simply contents himself with the following comment upon them:“ I will not seek to reconcile these two versions. I will leave to Mr. Challis the task ofexplaining how the name of Adams, which did not figure in his first communication, isbecome so prominent in his second.” Now, what are the real facts of the case? In theComptes Rendus , tome xxiii. p. 764, there appears a letter from Professor Challis to M.Arago, dated the 5th October, 1846, in which the writer gives an account of his searchfor the planet with the Northumberland telescope, and mentions his having detected itby its disk on the evening of the 29th September. In this letter he alludes to M. LeVerrier in the terms quoted by M. Arago as above stated. Again, in a letter to the editorof the Athenaeum, dated the 15th October, 1846, (see Athenaeum , October 17,) ProfessorChallis gives an account of the laborious search undertaken by him, having for its objectto detect the planet by its zodiacal motion. In this letter he states that he was guided inhis search by a paper which Mr. Adams drew up for him; that he commenced his obser-vations on the 29th July; and that a comparison of the observations of the 30th Julyand 12th of August, instituted subsequently to the receipt of the accounts of Galle’s dis-covery, shewed him that he had secured the planet. The reader will at once perceivefrom the foregoing statements that the two communications of Professor Challis referredto two distinct modes of search prosecuted on two distinct occasions. In his letter to M.Arago he mentions the result of observations pursued with the view of detecting theplanet by its physical aspect , professing to have been guided by the instructions of M. LeVerrier. In his letter to the Athenaeum he communicates the result of observationsanterior to the preceding that had been made with the view of discovering the planet byits zodiacal motion , asserting to have been guided on this occasion by Mr. Adams. Itwas impossible that the instructions contained in M. Le Vender’s paper of the 31stAugust, and first made known to Professor Challis on the 29th September, could havebeen of any service to that astronomer in a search for the planet prosecuted by him in thebeginning of the former of these months. A mind much less acute than M. Arago’s will,therefore, see no inconsistency in the two passages which that illustrious philosopherappears to despair of reconciling together. How justly may we remark in his own words,“ L’ amitie est souvent aveugle, et se laisse fasciner.”

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