[ 296 •] 
other planets, which aft more* or lefs upon the 
comet, as they do upon each other. In lliort, it 
was neceffary to confider all the different lituations 
and diffances of all the pJanets with regard to the 
comet, during the whole of its laff revolution, and 
even during the former ones, when the returns had 
been found to be unequal. 
What immenfe labour ! and what geometrical 
knowledge did this tafk not require? Mr. Clairaut, 
of the Royal Academy of Sciences, undertook it; 
and his refults differed but one month from the ob- 
fervation. No fraall degree of exaftnefs this, con- 
hdering the immenfity of the objeft. In November 
1758, he publifhed his conclulion, which allowed 
about 618 days more for the period that was to end 
in 1759 than for the former, whence he inferred 
that the comet muff be in its perihelion towards the 
middle of April. He added, however, {journal des 
S^avajis^ Jan. 1759) “ Any one may think with what 
“ caution I venture upon this publication, fince fo 
** many fmall quantities unavoidably neglefted by 
“ the methods of approximation may very poflibly 
“ make a month’s difference, as in the calculation 
“ of former periods.” It accordingly proved fo, the 
comet having reached its perihelion on the 1 3*^ of 
March in the morning. Mr. Clairaut has fincc 
publiflied the methods and calculations, by which he 
has arrived at this conclulion. 
The impatience of aftronomers, and their defire 
to prepare for verifying this prediftion of Dr. Halley, 
had put them upon enquiring for feveral years in 
what part of the heavens this comet was likely to 
appear ; but, being ignorant of the exaft time of its 
return. 
