Meajure of the Meridian in France, (sfc. 323 



Four commiflioners were fpecially charged with the computation of the triangles, which 

 they performed feparately, by different methods, in order to leave nothing doubtful as to the 

 certainty of the refults. They have' alfo calculated, and in every cafe by different methods, 

 the four portions of the meridian comprehended between the places at which the latitude was . 

 obferved ; namely, the terreftrial arc comprehended between Dunkirk and the Pantheon at 

 Paris ; the Pantheon and Evaux; Evaux and Carcaffonne; Carcaffonne and Montjouy. The- 

 details of thefe calculations, and the principles on which they are founded, are contained in a 

 memoir depoflted in the archives of the Inftitute*. 



Among other- conclufions which prefent themfelves in thefe calculations, there are two, to 

 which the attention of the Inftitute is direfted : the firfl:, that the mean degrees concluded for 

 the four intervals, of which mention is made-, all decreafe as they approach the equator ; and, 

 confequently, that this operation alone would prove the oblate figure of the earth, if this ar- 

 ticle required any proof: the fecond, which was far from being fufpefbed, and exhibits a very 

 remarkable phenomenon, worthy of the enquiries of the mofl: profound mathematicians, that 

 thefe fame degrees do not follow a gradual diminution, but decreafe at firft very flowly, be- 

 tween Paris and Evaux, only two modules for a degree of latitude ; afterwards very rapidly, , 

 namely, fixteen modules for the degree of latitude between Evaux and Carcaffonne, and that 

 this rapid diminution becomes lefs between the laft-mentioned town and Montjouy, beino- no 

 more than feven modules f. 



This remarkable fa6l is intimately connected with another, namely, that there are differ- 

 ences between the azimuths calculated for Bourges, Carcaffonne, and Montjouy, from that 



* The meridian between Dunicirk and Montjouy, which fubtends- a ccleftial arc of 9,6738 degrees, and of 

 which the middle point paffcs through 46° 1 1' 5" of latitude, is equal to 275792.36 modules. 

 That is to fay ; 



1. The diftance between the parallels of Dunkirk and the Pantheon, the • Modules, 

 middle point of whicfe lies in lat. 41/ 56' 30", fubtsnds an arc of z^.tSgio and meafurcs 62472.59 



2. Thr d'ftance between the parallels of the Pantheon and Evaux, the 



middle point of which lies in lat. 47° 30' 46", fubtends an arc of 2.66363 and taeafures 76145.74 



3. The ttiftante between the paraliels of Evaux and Carcaffonne, the mid- 

 dle point of which lies in lat. 44' 41' 48", fubtends an arc of i. 96336 and meafures 84424.55 



4. The diftance between the parallels of Carcaffonne and Montjouy, the 



roidd'e point of which lies in lat. 42° 17' 20", fubtends an arc of .1.85266 and meafures 52749.48 



Whole celeftial arc 9.67380 Meafur£ 275791.36 



+ If from the four intervals before given, we dedace thf mean degree, which may be concluded from the 

 fpherical hypoihefis, which is fufficient for a curfory view, we fliali find the mean dcgr«e in round members 5 . 



Modules. Difference. ^'^'"/^^ f".' • 

 pne degree. 



Bstvyeen Dunkirk and the Pantheon, mean latitude, 49<' 56' 30". 28538 5 2 



Between the Pantheon and Eraux, rapan latitude, 47 ''30' 46'/. " 18533 44 16 



Between Evaux and Carcaffonne, mean latitude, 44' 41' 48". 28489 12 7 ' 



Between Carcaffonne and Montjouy, mean latitude, 42* 17' iq", 28472 



of 



