178 On the Arcs perpendicular to the Meridian^ 



the persons who have conducted the observations, and who 

 are charged with the subsequent calculations, as they deem 

 themselves to have satisfactorily deduced from the observed 

 elements, and which will be ultimately justified by the publi- 

 cation of the elements themselves. For this purpose, reports 

 have been drawn up by the superior officers of the Corps des 

 Ing6nieurs-g^ographes, charged with the operations within 

 the territory of France on both the parallels, and have been 

 published by order of the French government, in the eighth 

 volume of the Memorial Topographique et Militaire redige 

 au D^pot General de la Guerre. 



A memoir has also been printed on the measure of the arc of 

 the parallel of forty-five degrees, which had been previously 

 read to the Academy of Sciences, by Colonel Brousseaud, of 

 the Ingenieurs-geographes, and M. Nicollet, membre du 

 Bureau des Longitudes, who had been employed in the deter- 

 mination of the celestial arc of that parallel comprised within 

 the limits of France. By the courtesy of the French govern- 

 ment, copies of the eighth volume of the Memorial Topogra- 

 phique et Militaire have been received by individuals in this 

 country, who have been engaged in operations, or in investi- 

 gations having the same ultimate purpose ; and by the per- 

 sonal kindness and attention of M. Nicollet, copies of his 

 highly interesting memoir have also been received. We avail 

 ourselves of the occasion to make more extensively known in 

 England the progress of undertakings, in the accomplishment 

 of which several of the principal states of the continent are 

 united ; as well as the decided tendency of the results which 

 have been hitherto obtained, to indicate, in accordance with 

 Pendulum experiments, and the general deduction from the 

 best arcs of the meridian that have been measured, a much 

 greater compression than - J <-, in which, until the last three or 

 four years, the general belief appeared to be almost fully 

 established. 



We shall commence with the arc of the parallel of forty- 

 five degrees. The western extremity of this arc is determined 

 by its intersection with the meridian of Marennes, a town of 

 France, on the shores of the Atlantic, situated a few miles 

 north of the discharge of the waters of the Garonne. Tra- 

 versing France, Piedmont, and Northern Italy, and connecting 



