from the measurement of an arc of the meridian , &c. 513 
Put 5 == ----- -f* i Sin. 2 A' — ^ . Sin. 2 A = , 3176258 
5 # = -f | Sin. 2 A'"— | . Sin. 2 A"=, 0738689 
arc be- f Punnae and Daumergidda, 
l J tween I Montjouy and Dunkirk. 
34 8 3955 
9820,8 
— 1 — nearly. 
s' L — s V 
rs 1 — r's 
r' L — s V 
rs' — r's 
e _____ r' L — r 1 / 
a ~~ FTTH sL‘ 
In the paper which I sent to the Asiatick Society, and 
which will appear in the 13th volume of their Researches, 
the terrestrial arc between Barcelona and Dunkirk, as given 
in the 2d volume of Colonel Mudge's Survey, was made use 
of, and is there stated to be 587987 fathoms, which gives the 
compression by this method But there must be some 
mistake in this ; for by comparing it with the distance 
between Montjouy and Dunkirk, as given by De Lambre, 
the former is considerably greater than the latter, though 
Montjouy is 3" south of Barcelona. The mean degree for 
latitude 47 0 24/ used in that paper for determining the 
ellipticity, compared with the Indian measurements, was 
deduced from that arc, and gave the compression -—i—, while 
the general mean compression obtained by comparing these 
measurements with the French, English, and Swedish de- 
grees, was nearly. 
Since it is here determined to adopt -j-i- as the compres- 
sion, and 60491,46 fathoms for the measure of the degree 
* See vol. iii. p. 89. Base du Systeme Metrique, where the arc between Montjouy 
and Dunkirk is 551583,6 toises, or 587657,17 fathoms, at the temperature of 32®, 
which reduced to the temperature of 62°, will be 587475,41 fathoms. 
