on Capt. Sabine's Pendulum Observations. 125 



trifling extent by the error alluded to. But he has not men- 

 tioned what effect this error has occasioned upon the experi- 

 ments at other stations, which depend upon the accuracy of 

 the observations made with the circle. Neither has he taken 

 any notice of the corrections to be applied to his computations 

 of latitude, although it is evident from the slightest inspection 

 that in many instances they are considerable, and must de- 

 stroy the remarkable accordance between the single results at 

 the same station. 



Several of the latitudes were obtained from observations of 

 southern stars, and depend on the accuracy of their calculated 

 positions. Capt. Sabine seems to have taken their right ascen- 

 sions and declinations from Mr. Lax's Nautical Tables ; but at 

 the time when that useful work was published, the positions 

 of the southern stars invisible in Europe were not accurately 

 known, as they had not been observed since the time of La 

 Caille. We are now in possession of more correct catalogues 

 of these stars, founded on the observations of Mr. Fallows at 

 the Cape of Good of Hope (Philosophical Transactions for 

 1 SS^), and of Mr. Rumker in New SouthW ii\es{ Astrojwmische 

 Nachrichten, No. 82). From the subjoined comparison it will 

 be seen that the apparent places assigned by Capt. Sabine to 

 the first two stars, differ very materially from those obtained 

 b}' computation from the catalogues of those astronomers. 



It is hoped that Capt. Sabine will see the propriety of 

 revising his computations and publishing the results ; for it is 

 not improbable that the alteration which has been made upon 

 one of the principal elements of his experiments may exercise 

 a considerable influence upon the deductions made from them : 

 at any rate it must be admitted that at present a certain de- 

 gree of doubt attends his observations, which ought to be re- 

 moved. In the mean time it may be said that he has much 

 overrated the accuracy attainable by the six-inch repeating 

 circle, the performance of which it is now seen does not sup- 

 port the eulogium pronounced upon it. And if the observa- 

 tions of latitude at the island of St. Thomas be held as a test 

 of the accuracy of the repeating reflecting circle, it cannot 

 be considered so perfect an instrument as would appear from 

 the published accounts ; for the two observations of latitude 

 (when the declination of a Crucis is corrected) will be found 

 to differ half a minute from each other. 



Apparent /It. App'.Decl. 



aCrucis, June 7, 1822, Sabine, 12'' 16'"52»-4 62" 6' 44" 



Fallows, 12 16 47-1 62 7 19 



Rumker, 62 7 17 



« Centamiy 



