[ * 5 8 ] 
of the orbit of Venus being almoft circular; the 
menftrual parallax would affeft the place of Venus, 
in that fituation, by a quantity not Jefs than 92" ; and 
in all other lituations in proportion to her didance ; 
which alfo holds with refpedt to all the red: of the 
planets. 
Thefe didurbing quantities are by no means to be 
difpenfed with, in the nice and critical date that 
adronomical obfervations and calculations have arrived 
at, in confequence of the difeoveries of Dr. Bradley, 
who may be laid to have given a bafis to adronomy ; 
however, could we rely upon the data , on which Sir 
Ifaac’s invedigation of the relative gravity of the Earth 
and Moon is founded, wefhould have nothing to do 
but to apply an equation to the particular cafes, ac- 
cording to the diameter of the epicycle, as deduced 
from the relative gravity ; but whoever confiders the 
great obdru&ions that the water of the fea meets with 
in its motion to obey the influence of the Moon ; the 
great difficulty in afeertaining the true height of the 
tides, from the many diflurbing caufes intervening y 
and the many uncertainties, and want of coincidence, 
that have attended, and mud attend, fuch obferva- 
tions; mud confefs, that this matter does not feem 
capable of fuch a determination from that quarter, 
as the prefent date of adronomy requires. 
Accordingly, flnee the time of Dr. Gregory, thofe 
great aflronomers Dr. Bradley, De la Caille, and 
others, have applied themfelves to determine the quan- 
tity of the mendrual parallax from folar obfervations: 
but though thefe have given enufe to fuppofe that the 
relative gravity of the Earth and Moon are not above 
of the quantity deduced from the tides ; yet, as the 
©bfervation 
