128 A curfory Tlew of fotne of the 



The French afironomers have at length terminated the 

 grand operation of meafuring an arc of the meridian from 

 Dunkirk to Barcelona. They performed this labour with 

 fvich precifion, that no fenfible error can be fuppofed in it, 

 efpccially as their refults are abfolutely agreeable to thofe 

 given by preceding meafureraents. It appears from their la- 

 bour, that the quarter of (the terreftrial meridian, that is to 

 fay, the arc of the meridian comprehended betweer. the Equa- 

 tor and the North Pole, is = 2,561,370 modules, (they have 

 employed this word to exprefs a ruleof platina of twelve feet, 

 or two toifcs,) which make 5,122,740 toifes. The metre is 

 the ten millionth part of this quantity; that is to fay, the 

 length of the metre is -rVcVoyo parts of the module ; and, by 

 comparing this with the ancient meafures, the true metre is 

 443 rVA- ^"^*^^ "^ the toife of Peru, (that is to fay, of that 

 which ferved the French academicians for meafurlng a degree 

 in Peru,) the temperature of this toifc being fuppofed to be 

 18*' of Reaumur, or 16^- of the centigrade thermometer. 

 The metre, therefore, is 3 feet 11 -rWfy lines. 



They have calculated alio the length of the degree for the 

 different latitudes which they meafured. The following is 

 the refult : — 



The degree between Dunkirk and Paris 

 in the mean latitude of 49'' ^6 30", is - 



Between Paris and Evaux, in the mean 

 latitude of 47° 30^ 46" _ _ _ 



Between Evaux and CarcafTonne, in the 

 mean latitude of 44° 41 ' 4'^ - - - 



Between Carcaffonne and Montjouy, in 

 the mean latitude of 42° 17' 20" 



This length of the arc of the meridian is the fame as that 

 before determined by obfervations. The following is the 

 account given of it by Lalande * : 



" In obferving carefully with a fcxtaat the zenith diftance 

 of the fame ftars at Paris and at Amiens, there has been 

 found 1° l' 13''' of difference in all the altitudes between two 

 points, the diftance of which deduced from the preceding 

 was 58233 toifes. Nothing remains, therefore, but to make 



• See his Alironomy, third edition, No, 2661. 



the 



