BowditcJi on the Ohlateness of the Earth. 



that wc ouglit to obtain a more correct value than by any other 



w ay 



The next method in point of accuracy would be by the ob 



depending on the actual 



served lengths of pendulums, and that 

 measures of the degrees of the meridiuus, which at first sight ap- 

 pears to be th^ most natural and accurate, would be in fact the 

 least accurate of any of the methods here mentioned. 



To obtaiu the oblateness by meaus of the lunar equations^ the 

 iadefatigable Astronomer Uurg undertook to compute the coelli- 

 cients of these equations by means of such of the observations of 

 Maskelyne, as were proper for that purpose^ and from these values 

 La Place lias computed* the oblateness of the earlli. The equa- 



tion in longitude made it 



1 



30j,a5 



and the equation in latitude 



1 



w hich differ from each other but a very small fraction^ and this 

 wonderful agreement of two independent calculations is a great 

 proof in favour of the accuracy of the method, and of the correctness 



^> 



of the result ; and if we neglect the decimal parts of these num- 



I 



bers, we may put ^-— for the oblateness as determined by this 



'^OJ 



method, and in all probability this is very near to its correct val- 

 ue; we should therefore be led to infer from what has been said, 

 that the oblateness determined Hy the observations on the pendu- 

 lums would agree very nearly with this quantity ; but according to 

 La Place's calculation this is not the case. For by combining all 



the observations of the pendulums which he considers as sufficient- 

 ly correct, he has found the oblateness to be — r-.^,! which differs 



* In Book VII, § 24, 25. 



t This is given in Book III, § 42 of his " MScaniqiie Celeste** Making use 

 ©f the observations in Peru, Porto-Bello, Pomlicherry, Ja-aaica, Petit-Goave, Cape 

 of Good Hope, Toulouse, Vienna, Paris, Gotha, London, Petersburgh, Areasgberg, 

 Ponoi, a^d Lapland. 



% 



.."*, 



