ISS Dr. Gregorifs Strictures on Don Rodriguez. 



be found in the estimate of the entire arch, and will in- 

 crease in proportion to the extent oF the arch measured : 

 but in the English measiir^fment we find exactly the reverse 

 of this." Here he assumes the principle proposed by Bos- 

 covich, but condemned by Laplace, for a reason thus briefly 

 assigned by Puissant: — "La solution donnee d'abord par 

 Bostovich est viclense en ce qu'elle est fondee sur une hy- 

 pot/iese inadmhsiHe, savoir, que les crreurs dans le mesure 

 des arcs du meridien sont proportionelles a. leurs lon- 

 gueurs." 



5. Be concludes that there must be " an error of some 

 seconds in the observations of the fixed stars," because 

 " the results of the observations made on different stars 

 differ no less than four seconds from each other." Now, 

 what are the facts on which this inference rests ? Simply 

 these: that the only two stars which indicate any such dif- 

 ference, in the whole series of observations, are [j, Draconis, 

 and ^ Ur?ae ; that they give a difference of 4-"l9, not in 

 the aniphtude of the arc between Dtmnose and Arhury Hill, 

 but of that between Dunnose and Clifton; and that whether 

 those two stars be rejected, or retained with the olherjifteen 

 employed in finding that amplitude, they will not occasion 

 a difference of a quarter of a second in the result. How^ 

 then, can a fair investigator bring this as a reason for an 

 alleged inaccuracy, when it obviously cannot apply to the 

 case? And what must be thought of his impartiality, if it 

 shall appear that eve7i iv this respect the observations of the 

 French and of Major Lambton, which he so manifestly 

 prefers to the English observations, are far more open to 

 censure ? Allow rae, therefore, just to make the com- 

 parison. 



Of the English observations none are suppressed, (the 

 observers going upon the principle explained by Simpson 

 in his " Tracts," v.'hich clearly establishes the propriety, if 

 not the necessitv, of taking the mean of a number of ob- 

 servations,) and yet no irrcgularitv of consequence, except 

 the one above specified, appears. But, it may be seen from 

 p. 72, Discours Prcliminaire, tome i. Base dii Systtme 

 MctricjiLe Decimal, that no less then sixty-eight of the 

 French observations upon /3 UrsiE majoris were rejected, 

 and termed ^a'/; for no other reason that I can perceive, 

 than that if thev had been employed they wovdd have given 

 the latitude of Dunkirk about a second less than the obser- 

 vations of the pole-star gave it. Let Don Rodriguez re- 

 flect upon this, and then repeat that the French operations 

 " 7nertl the highest degree of confidence." But this is not 



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