[ 39 8 ] 
2 ^ f 
roid to turn about the axe is 2— 7r x t 8 7 ^ 5 . 
Which was to be found. 
Corollary. 
2. If it were required to find the fum of the mo- 
ments of all the points of a fingle crown E L^E 1 ZE, 
fig. I. n° i. placed at the equator, and detached from 
the earth, to turn about the axe of the circle of 
the fun’s declination, the thicknefs of the crown be- 
ing a a : 
The moment of the point L to turn about c is the 
fame as that of the point y to turnabout C y as is ma- 
nifeft from the refolution of the motion according to 
S L into two, Ly , and y S* ; and from the great 
diftance of the fun y S will not differ from L S 5 the 
triangle L y S being right-angled at y. 
By the preceding problem, if c L , or C Y ’ be called 
X- } and C c 1 , Y ; and all the other denominations of 
that problem be retained ; we fhall have yx. = Xu y 
zndCx. = XY. 
And the moment of the point y is y x 
y x x S x 3 Cx(=*j— 
And putting inftead of y , the element of the crown, 
which is a a x d calling, in this cafe, d u the ele- 
ment of the circumference ELQE\ the moment 
of an element of the crown will be arz x x Vu x 
j 3 
* The lines S L and yS are not drawn in the 7%. to avoid con- 
fu’ion. 
XX chi 
