VOL. LXXTIl.] 



PHILOSOPHICAL TRANSACTIONS. 



23g 



Hence the difference of meridians of the two Royal Observatories, by the ob- 

 servations made in the Royal Observatories themselves, is Q^ 30^; and by the 

 observations made by M. Messier, at the Hotel de Clugny, and reduced to the 

 Royal Observatory, is Q™ 20^ The mean of both results is 9™ 25^ But if 

 greater weight be given to the latter determination than to the former in the 

 ratio of 2 to 1, on account of the series of M. Messier's observations being the 

 more complete, the difference of meridians will be 9™ 23^ 



M. du Sejour, in the Memoires of the Royal Academy of Sciences for 1771, 

 found 9™ 20", as well from the beginning as end of the solar eclipse of 1 769. 

 M. Mechain, the learned editor of the Connoissance des Temps, informs me, 

 that from the immersions of Celeno and Maia at the moon's limb, on March 5th 

 last year, he has found by calculation from M. Messier's observations compared 

 with mine, g^ 19^9, and 9"^ 17\Q, or by a mean 9"" 18^9; but by his own ob- 

 servations compared in like manner, he makes it a little more than 9"^ 20^ He 



