9± 



FIGURE OF THE EARTH. 



the perpendicular too great by 200 fathoms, but this arises from 



a mistake in his calculation. 



By applying Lastly; I shall apply the same method, and see how nearly 



thod a of e C om- tIie e,5i P llc hypothesis agrees with the last measures taken in 



puting the arcs France, which merit the highest degree of confidence, both 



in seconds and w j tn reS pect to the observers who have executed it, and the 



in toises, the ■ " i 



elliptic hypo means which they had it in their power to employ. I have 



to^'Vee w^rf taken only the arc between Dunkirk and the Pantheon at Paris, 

 the fate mea- from the data published by the Chevalier Delambre in the 

 sures taken in 3t j vol. of the Measurement of the Meridian. I employed 

 the same elements and similar calculations to those made on the 

 English arc. The oblateness of T ^ gifes the difference between 

 the parallels equal to 7383,615 seconds by the eastern series of 

 triangles, and 7883,617 by the western series. The mean of 

 these 7883,616 may be taken as the true extent of the total arc. 

 The two other elements give for this quantity, 7883',62l 

 and 7883",4p3, or 2° 1 1' 23",6 and 23",49, as the calculated 

 extent of the arc. But the arc observed was 2 e ll' ic>",83, 

 according to M. Delambre, and 2° 1 1' 20",85 according to 

 M. Mechain j so that the least difference between the cal- 

 culation and the observations will be 2",64. M. Dehmbre 

 is of opinion, that the latitude of Dunkirk, which is sup- 

 posed to be 51° 2' 9",20, should be diminished; and in fact 

 the distance between the parallels of Dunkirk and Green- 

 wich, which is 25241,9 toises, gives by the mean of the three 

 assumed elliptiticies 26" 32\3 for the difference of latitude. 

 After deducting this quantity from 51° 28' 40'', the supposed 

 latitude of Greenwich, there remains 51° 2' 7",7 or 8", for 

 that of the tower at Dunkirk. If from this again we deduct 

 the calculated arc 2 Q ll' 23",5, we have 48° 50' 44 7 ,5 for the 

 latitude of the Pantheon, while, according to the observations 

 of M. Delambre, it is 49", 37, or 48",35 by those of M. Me- 

 chain. If various circumstances, with regard to unfavourable 

 weather, and also others of a different kind connected with 

 the revolution, and of which M. Delambre complains with 

 much reason, have occasioned some uncertainty with respect to 

 the obser rations at Dunkirk, still the numerous observations 

 made at Paris, both by him and by M. Mechain at a more 

 favourable season, and in times of perfect tranquillity* render 

 the supposition of an error of 4 seconds in the latitude of the 



Pantheon 



