,1 . . MEASUREMENT OF AN ARC 



degree due to latitude 9® 34' 44" and in that due to latitude 16^ 14'42", 

 (which Will according to this alteration come out 60507,19 fathoms) 

 may be determined. And it appears that the firfl is 23 fathoms in 

 def-ft, and the other 5.59 fathoms nearly, in excefs; both very fmall 



quantities, the greateil being kfs than J- of a fecond .on the earth-'s 

 furfacCu 



With refpe^i; to the compreSon, it is impoHible that ^-^^ canlye 

 -very far from the truth, fmce the whole of the meafurements which 

 are entitled to the greatefl: confidence, are taken into account. The 

 French mathematicians, by ufing Bouguer's meafureraent at the 

 Equator with their own, have found the com pre (lion to be ^\-^ nearly. 

 But if ih^ic -Indian meafurements be correct, Bouguer's degree at the 

 equator is 23 fathoms io excefs. I have the highest opinion of that 

 fagaciousobser vet's who appears to have been the moft correct of all 

 the academicians sent out at that tmie, and the only one apprized of 

 the effect of local attraction on the plummet. But to obferve in {& 

 mountainous a country, and with an inftrurnent far inferior to thefe 

 now in use, an error of that, magnitude is not to be coofidered as lur^ 

 priiing; yet it will make a confiderable difference in the compreffian. 

 The celebrated La Lande in all his aftronomicalobfervations, where 

 the figure of the earth was concerned, invariably u£ed ^-^ ; and if 

 this betaken in.computing the preceilian of the equinoxes, and the 

 effect of folar Butation, the theory will very nearly agree with obferva« 

 tion. The compreifion is an element of: very general importance in 

 the higher branches of phyfical aftronomy ; and it is gratifying to 

 -think that the quantity deduced from thefe recent combined meafure- 

 ments is nearly" that which has been adopted by the ablest aftronomers, 

 10 make the theory agree with obfervation. 



