5 MEASUREMENT OF AN ARC 



never happen. I am of opinion, that fufEcient. has been done for 

 eftablilhing the points in queflion, viz. the eUiptical figure, and dimen- 

 fions of the earth, the great objects of all the meridional operations, 

 efpecially thofe recently performed, which in grandeur and accuracy 

 must be allowed to exceed any thing of the kind recorded in the hiilo- 

 ry of practical fcience. The great excellence of the inftruments nowr 

 in ufe is the chief caufe of this faperior accuracy ; and it is by that 

 fame excellence that irregularities have been difcovered which former 

 obfervers were not aware of^. and therefore not prepared to guard. 

 againll; and the univerfal principle of attraftion, which has long been 

 ellabhihed, is now found toaffed; the plummet of a zenith fector, and 

 where there is any unequal force acting in the diredion of the meri- 

 dian^ occafioned either by mountains or by different deniities of the 

 ftrata lying to the north and south of the ftation of obfervation, ths 

 plummet of the fector will be drawn from its vertical pofition. The 

 French and Englf/h operations have been confiderably dillurbed by 

 this invifible agent ; for fo it may be termed, when no mountains are 

 near ; and ray former obfervations at Dodagoontah, Bomafwidrumt and 

 P^M^/iz^r have witneiled its effectSa^ Having however, left ouc thofe 

 ilations altogether, the obfervations at Punnalf Putckapolliam, Namtha' 

 bad, dind Daumergidda, appear to have been entirely free from any 

 anomaly, a circumilance which mud give a preference to thefe extent 

 five operations over any of the prefent day. 



After having- determined the ratio of the polar axis to the equato- 

 rial diameter, their actual lengths are thence obtained, and finally the 

 length of the quadrantal arc of the meridian, from which the French. 

 mathematicians have deduced their ftandard; the io,ooo,oooth part of 

 which are reduced to inches, being their ijutre or unit of meafure. 

 The meafure of the mdre.hQi^ brought, is 39,37,08 EngH^h inches at the 



