$G *T6URE OP THE EAltTH. 



recting the declination, but remain uncorrected in the latitude 

 of each. 



bVbirtha^ht" Lieutt Co1, Muc, S e is also of opinion, that the irregularity in 

 error on the the value of his degree may be ascribed to deviation of the 

 English arc plumb-line, occasioned by local attractions. This is certainly 



may be in the J * 



observations, very possible, and may be decided by an examination of all cir- 

 cumstances on the spof. But if there be really an error of 1" in 

 the extent of the whole are, this should rather be ascribed to 

 some defect in the observations themselves than to any extra- 

 neous source ; for the observations of different stars give results 

 that differ more than 4 seconds from each other. 



Measurements l shall now conclude this Memoir, by expressing: a wish, 



stillwantingin ... e . _ . , . . ... 



the southern which men of science m England have it more in their power 



hemisphere, than any others to gratify j I mean by making new measure- 

 ments in the southern hemisphere. Those which have been 

 made hitherto in the northern hemisphere are extremely sa- 

 tisfactory by their agreement, and give us great reason to 

 presume that the general level of the earth's surface is ellip- 

 tical, and very regularly so j and hence we might expect the 



- opposite hemisphere to be equally so, and to be a portion of 



Fqrthemea- , ^ T , , , V, 



sures of La- tne same curve. Nevertheless, the degree measured at the 



cailleseem to Cape of Good Hope by Lacaille, is latitude 33° IS' appears to 



indicate an el- . ,. ... c , . . . . 



lipseof lessee- indlcate an ellipse or less eccentricity, or of greater axis ; for 

 ecntneity. the linear extent of 5/Q37 toises, corresponds to the measure 

 of a degree in latitude 47° 47' in the northern hemisphere. 

 Jf now we calculate the arc as before, with an oblateness of 

 1 _4_, and with the sides of Lacaille's triangles reduced to the 

 meridian, we find it greater by 10" than it was found to be by 

 observations of the stars. An error of 10 seconds, by an 

 astronomer so skilful and scrupulous as Lacaille; is too extraor- 

 nary to be admitted as probable. It is true, that there was a 

 greater error well ascertained to have occurred in the measure- 

 ment in Lapland, amounting to 13 seconds j but the academi- 

 cians engaged in this undertaking were by no means equally 

 conversant with observations as Lacaille. / 



Proposed ad- There remains, therefore, but one method of removing all 

 measurement doubt on this subject, and this is to repeat and verify the mea- 

 surement at the Cape, and, if possible, to extend it still farther 

 to the north. The same Major Lambton, who has succeeded 

 so well in Asia, and is in possession of such perfect instruments 



for 



