[ i6 3 ] 
will be at full, not above 1 2 hours preceding that 
oppofition, the Moon will be nearly in the mod 
favourable fituation for the purpofe. 
For this end, let an accurate obfervation be made 
upon the place of Mars at the following times, viz. 
fird, near the time of the new Moon, preceding Mars’s 
oppofition ; or more properly at the neared opportu- 
nity, to the time of the Moon’s oppofition to Mars j 
which will happen in the night, between the 12th 
and 1 3th of October : fecondly, let the place of Mars 
be obferved when the Moon is neared her quartile 
with Mars; that is, between the 19th and 20th of 
the fame month : thirdly, let an obfervation on Mars 
be made when the Moon is in conjunction with Mars, 
the neared to his oppofition with the Sun ; that is, 
between the 23th and 26th of ditto: fourthly, let 
Mars again be obferved when the Moon has moved on 
to her quartile with Mars, viz. between the 3 id of 
OClober, and id of November : and fifthly and ladly, 
let the place of Mars be obferved, when the Moon 
has again got to her oppofition with Mars, which hap- 
pens between the 7th and 8th of November. 
Now it is manifed, that, when the Moon is 
in conjunction or oppofition to Mars, the cen- 
ter of the Earth, the center of Mars, and the 
common center of gravity of the Earth and Mars, 
will be nearly in a right line, and confequently, that 
an obferver will then fee Mars, in the fame place in 
the heavens, as if the common center of gravity was 
the fame as the center of the Earth ; therefore, then 
the place of Mars will be unaffected by a mendrual 
parallart; and fuch will be the fird, third, and fifth 
of the obfervations above propounded. 
