342 Bon J. Rodriguez's Observations on the 
reason to suppose a greater error than one second in the ob- 
servation of each azimuth, and it seems next to impossible to 
arrive at greater exactness. 
The difference of longitude between the points A and B is 
48' 57", 3b. With this angle and the co-latitude at A, we have 
in the spherical triangle right angled at the point A, the ex- 
tent of the normal arc equal to 2867,330 seconds, and dividing 
its length in feet by this number, we have for the degree 
perpendicular 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 
3~o or -3-t- ; and in short, the correspondence between the hy- 
pothesis and the measures of Major Lambton, is as complete 
as can be wished. Major Lambton, indeed, finds the degree 
on the perpendicular too great by 200 fathoms, but this arises 
from a mistake in his calculation. 
Lastly, I shall apply the same method, and see how nearly 
the elliptic hypothesis agrees with the last measures taken in 
France, which merit the highest degree of confidence both 
with respect to the observers who have executed it, and the 
means which they had it in their power to employ. I have 
taken only the arc between Dunkirk and the Pantheon at 
Paris, from the data published by the Chevalier Delambre in 
the 3d 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 gives the difference 
between the parallels equal to 7883,615 seconds by the east- 
ern 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", 62 1 
