ij8 M, de Zach's Agronomical Obfervations. 
large telefcopes, which magnify too much, and give too great a 
trail lit between the penumbra and the true dark Ihadow. On 
that account fome celebrated aftronomers advife to ufe for the 
eclipfes of the moon no greater telefcopes than of four or five 
feet length. It was remarked at Paris, that in an eclipfe of 
the moon, obferved through a telefcope of D©LLOND,the focus 
of its object lens being 30 inches, and likewife through a tele- 
fcope of five feet length ; the eclipfe appeared to begin V 7" 
fooner, and to end 4' 7" later, through the final! than- 
through the long telefcope; the like has- been remarked by 
fever al others, and it has been alfo -obferved by myfelf. As to 
my older vations I am tolerably fatisfied with them,, as they do not 
differ materially from thofe of Father le Fevre, though it is. 
known that in eclipfes of the moon no greater exachiefs than 
that of a minute can be obtained. The moon’s fpots were 
carefully obferved; for it is known, that the mean of the ob- 
fervations of the moon’s fpots is fuffieient to afcertain the 
longitude of a place to 4" or 5 nearly. M. de la Lande 
comparing the obfervations of the moon’s fpots in an eclipfe,. 
made the 2 2d of November, 1760, in Vienna, by the Impe- 
rial Aftronomer Abbe Hell, with thofe made at the fame 
time in Paris by M. Messier, finds the difference of meri- 
dians to be 56" 13", which agrees very exa&ly with that, afcer- 
tamed by other means. 
Correfpondent 
