[ 106 ] 
the ftars themfelves : from whence the angular 
diftances of the ftars muft vary in proportion to the 
velocity of thofe motions, or to the direction of thofe 
motions with refpedt to ourfelves. I have reafon, 
at prefent, to believe that a fmall motion may be 
difcovered in the ftar o Ceti, and perhaps in other 
ftars that vary in degrees of brightnefs, which the 
diligence of future aftronomers will difcover, and 
perhaps in lefs time than at firft fight might feem ne- 
ceffary, when we confider the feveral improvements 
which have of late been made in the methods of ob- 
ferving the heavenly bodies. 
As the motion of Ardturus in declination (the 
quantity of which we have thus endeavoured to as- 
certain) has been often acknowledged, it is matter 
of wonder that fome aftronomers, by comparing 
either the altitude or zenith diftance of the Sun’s limb 
with Ardturus, without previoufly fettling the quantity 
of that ftar’s motion in declination, or at lead: doing 
it indirectly, fhould endeavour to determine whe- 
ther the obliquity of the ecliptic hath remained con- 
ftant, orftill continues todiminith, as it fhould feem 
to have done for many centuries pad, from the obferva- 
tions of fucceffive aftronomers. Mr. Caftini, and 
Mr. le Monnier, have both pradtifed this method, 
and are of opinion, that the obliquity of the ecliptic 
hath not altered ; or, if it hath altered, that the 
quantity of its alteration is not near fo confiderable 
as hath been imagined by fome celebrated aftrono- 
mers. By obferving for feveral days before and after 
the folftice the altitude or zenith diftance of the 
Sun’s limb, and that of a ftar lituated near the fame 
parallel, the differences to be remarked in. procefs of 
time 
