[ 39 ] . 
fafely ufe the radius inflead of V wherever it 
occurs. 
By this means the general equation will become 
' / 
r—d V = or which is the fame 7 ' — dV~x y 
therefore V— but by prop. IV. V — 
* f jA — q'v ? 
which, becaule q is nearly equal to V, and q'u very 
/ 
fmall with refpedt to q A, will become V — ■„ 
therefore , from which we {hall find 
d A 
v = anc ^ ^is equation is exadly the fame 
with that which would arife from confidering the 
fun as a circular, and Jupiter as an elliptic plane, 
limited by one of bis meridians, and always parallel 
to the di Ik of the fun 5 which fuppolition, the im- 
menfe diftance of Jupiter from the fun renders very 
allowable. 
From this equation an eafy mechanical method, 
may be derived of delineating the curve of the fha- 
dow, at any given didance from Jupiter, for as y. de- 
notes any femi-diameter of the elliptic fedtion of Ju- 
piter’s body, it is manifed:, that the term y X will 
exprefs the correfponding femi-diameter of a fimilar 
ellipfis, whofe axes are to thofe of Jupiter in the 
given ratio of A to d 9 . and the term -y is wholly given: 
Therefore i {arm (fig. 7.) be Inch an ellipfis, and 
there be drawn through its center M any . number of 
femi-diameters Mr/, M Me, &c. meeting the el- 
lipfis 
