FIGURE OF THE EARTH. Q3 



Tence is rather less than in that of Lapland, although the 

 two arcs are very nearly of the same extent. Thus the de- 

 gree on the meridian measured in Bengal, in the latitude of 

 12^ 32' 21' north, cannot be supposed to exceed Major Lamb- 

 ton's estimate by more than 5,22 toises j and it is extremely 

 difficult to speak with certainty to quantities so small as this. 



The same observer also measured one degree perpendicular and also 



to the meridian, by means of a large side of one of his triangles from a '-csrree 



. ,. , .7^ , , , ,;. D . measured by 



cutting the meridian nearly at right angles, and of which he Major Lamb- 

 observed the azimuth at the two extremities. The data from ton » perpendi- 

 which his results may be verified are these : meridian. 



Length of the chord of the long side in English feet AB= 

 291197,20. 



Azimuth of the eastern extremity A equal to 87° 0" 7",54: 

 NW. 



Azimuth of the western extremity B equal to 267° 10' 44',07 

 NW. 



North latitude of A 12« 32' 12",27 

 North latitude of B 12° 34' 38",86. 

 With these data in the triangle formed by the long,side, the 

 meridian at B, and the perpendicular from B on the meridi an 

 at A, we have the chord of this last arc equal to 290845,8 

 feet, and the arc itself 290848,03 feet. By applying the me- 

 thod of M. Delambre, we find the azimuth of the extremity 

 B less by 2 " than it was observed to be ; so that we have no 

 reason to suppose a greater error than one second in the obser- 

 vation of each azimuth, and it seems next to impossible to 

 arrive at a greater exactness. 



The difference of longitude between the points A and B is 

 48 y 57",30. With this angle and the co-latitude a>t A, we hav« 

 in the spherical triangle right angled at the point A, the extent 

 of the normal arc equal to 2867,330 seconds, and dividing its 

 length in feet by this number, we have for the degree per- 

 pendicular to the meridian, at the extremity A, 60861,20 

 fathoms, or 57106,5 toises. Now these values are precisely 

 what we find on the elliptic hypothesis, with an oblateness of 

 T J Rr or -j A-g. j and in short, the correspondence between the 

 hypothesis and the measures of Major Lambton, is as complete 

 as can be wished. Major Lambton, indeed, finds the degree on 



the 



