GOULD — REDUCTION OP D'AGELET's OBSERVATIONS. 5 



virtuous and humane, and that his experience in such regions, least frequented and nearest 

 to a primitive condition, indicated that the human race is naturally kindly. It probably did 

 not occur to him that the first publication of a catalogue formed from his observations would 

 be due to the representatives of that region, when its coast should bo white with canvas and 

 its cliffs noisy with the echo of hammers and the hum of commerce. 



In J. Bernoulli's Nouvelles Litteraires de clivers Pays, Gainer I, p. 35, may be found an 

 article by d'Agelet in commemoration of M. de Mersais, a young astronomer who accom- 

 panied him in the Kerguelen expedition. 



$ 3. INSTRUMENT. 



The instrument which was used by d'Agelet in these observations was the same which 

 was subsequently employed by Lalande in his zones, and to which wo probably owe observa- 

 tions of a larger number of stars than to any other instrument known to astronomical history 

 previous to Bessel's zone-observations. Yet its peculiarities seem to have been little studied, 

 owing to the rough methods of reduction employed by Lalande himself, and to the circum- 

 stance that all the observations reduced by Bailt and Fedorenko were made in zones, each of 

 which was differentially treated, independently of the rest. 



It was a mural quadrant, constructed by Bird, in 1775-8, having a radius of 7J French 

 feet, and an aperture of 32 lines. 1 In dimensions aDd construction it seems to have been 

 similar to that of Lemonnier, and apparently a copy of the celebrated quadrant of Bradley. 

 Lalande, on page viii of the Histoire Celeste, says it has been described in his astronomy, 3 and 

 better still in one of the Cahiers des Arts of the Academy, published in 1774, by Lemonnier, 

 under the title, "Description des Principaux Instruments de V Astronomie." Since the paper of 

 Lemonnier was actually published before the instrument of d'Agelet and Lalande was made, 3 

 it may reasonably be inferred that the latter was intended as an exact duplicate of that one 

 to which the description originally referred. 



The limb of the quadrant was furnished with two independent graduations, the one being 

 into 90 degrees, and each degree into 12 parts of 5' each ; the other being into 96 divisions, 

 and each of these into 16 subdivisions, each of which corresponded, therefore, to an arc of 



> Mem. de l'Acad. 1789-191. 2 3d edit. II, 588, 684. 



3 In a note to the first page of the preface of the British Association's catalogue of Lalande'S stars, an apparent contradic- 

 tion ia alluded to, as follows: "At page ix, LALANDE, after mentioning an improved mode of supporting the telescope, says : 

 ' J 'ai oui dire autrefois que l'arc de ce quart de cercle avait etc rompu chez LEMONNIER, mais il a Cte parfaitement reiabli.' 

 Ilcnco one would suppose that the quadrant of the tcole Militaire was identical with Lemonnier's. This, however, is 

 distinctly contradicted by Lalande elsewhere, for, in speaking of the quadrant of the Ecolc Militaire, he says : ' M. Bergeret, 

 receveur-general, le fit faireama sollicitation par Bird des 1775, et en 1778, le coufia a M. d'Agelet,' {Mem. dc l'Acad. 1789,) 

 while Lemonnier's quadrant was made for him in 1753, at the expense of Louis XV. It would seem that Lemonnier's 

 quadrant was ultimately transferred to the Royal Observatory." The text of Lalande, although certainly rather ambiguous, 

 does not seem to me to imply such a contradiction. A few lines above be says that Mf.cii.un, having seen a contrivance for 

 relieving the center of the weight of the telescope, had engaged Lenoir to make this addition to the mural of the observatory. 

 Then, after describing the arrangement of the counterpoise, he makes the remark above cited concerning "this quadrant," 

 manifestly referring to the mural quadrant of the Paris observatory, which Lemonnier bad described, and not to the quadrant 

 of the Ecolc Militaire, used first by d'Agelet and then by Lalande. To this same note I am indebted for the title of the 

 work in which Lemonnier's description is published, but which I have not been able to find. — "Description des Arts et Metiers, 

 faitcs ou approures par MM. de V Academic Royale des Sciences Paris, 1761-89." 



(5) 



