C 389 ] 
But hitherto we have not confidered, that to the 
preceffion, thus caufed by the fun, we are to add that 
likewife produced by the moon ; and it remains, 
that we examine into the motion of the earth’s pole, 
caufed by the adtion of the moon on the redundant 
matter about the earth’s equator. 
All, that has been faid concerning the fun, is alike 
applicable to the moon, which we may put in the 
place of the fun ; the moon’s orbit in the place of the 
ecliptic ; and the time of the moon’g revolution round 
the earth in the place of the revolution of the fun 
round the earth : And we fhall find the motion of 
the earth’s pole parallel to the lunar orbit, which is 
always the fame at every quarter of the time of the 
revolution of the moon round the earth, and the ofcil- 
lation of the earth’s axe to the plane of the lunar or- 
bit, which is completed in each femire volution of 
the moon round the earth. 
But whereas the plane of the lunar orbit, which 
is always inclined to the plane of the ecliptic in an 
angle of about 5 degrees, never continues in a con- 
ftant pofition, like the plane of the ecliptic, fo that 
its pole defcribes a final! circle parallel to the ecliptic, 
at the diftance of about 5 degrees from the pole 
thereof ; it follows, that the preceffion, with refpedt 
to the lunar orbit, is not the fame as with refpedt to 
the ecliptic j and that the motion of the pole parallel 
to the lunar orbit ffiould be referred to the plane of 
the ecliptic : Which is done by rcfolving the motion 
of the pole, parallel to the plane of the lunar orbit, 
into two motions, the one parallel to the plane of the 
ecliptic, and the other perpendicular thereto, and in 
the plane of the folfticial colure. 
The 
