[ 427 3 
By this means we may apply all the formula 
which have been found in Sett. I. to the motion of 
the nodes of this ring, and to the alteration of the 
inclination of its axe to the plane of the ecliptic. 
But by the Remark on Art. 6. the motion of the 
plane of this ring is the fame, whether the ring be 
entire, or there be only a iingle point which circu- 
lates in the ring’s circumference : Whence it fol- 
lows, that 
Thefe fame formula do likewife give the motion 
of the pole of the orbit of a moon or fatellite ; the 
motion of the node of the orbit of fuch moon in the 
ecliptic ; and the variation of the inclination of its 
axe of the orbit to the plane of the ecliptic : Ob- 
ferving to put the time of the revolution of this moon 
about the fun, inftead of the time of the earth’s re- 
volution about the fun, and the motion of the moon 
in its orbit inftead of the motion of a point of the 
equator. 
Remark. 
It may be obferved, that although the motion of 
the pole of a ring be the fame as that of a moon, 
during the time of the revolution of the ring, or of 
the moon, which is the fame ; yet there are fome 
particular motions which take place when there is 
only one moon revolving in the circumference of the 
ring, and which ceafe to exift when it is an entire ring 
that revolves. 
For example; in Art. 2. the force, according to 
Ly , fig. i. n 2. of the point L, is deftroyed by an 
equal and diredtly oppoftte force of another point a 
placed on the other fide, and at the fame diftance from 
the point £, as the point L , when the ring is entire ; 
H h h 2 but 
