2C<

Astronomy.

Plate

LXII.Fig. 2.

t ; N X R 1 : v"r, (by Art. 13.) therefore N •

T v ' 01 jfji 1

15. In like Manner it is shewn, that if the *~Ao‘ ll jtal Area p r S of the Parabola p r q be divide® ^ e r 0*IOO equal Parts, and p S — r, and n =t ^ usP . fo

X

those Parts in the diurnal Area ; then n : —'•

T T T cp^S”

ft : n :: -A : A . * = N X -A, if R = S

Ri ri f'

or the Radius of the Earth’s Orbit. , e fi& s ’

16. On thesePrinciples the Comet ary Calculus e « •

, . _l>f ^

for in any Parabolic Orbit the. Quantity n —'

is the diurnal Area, and may therefore be est ee

1 Motion or Anomaly of the Comet for a Day ’ 0tiplied by the Time fexprefs’d in Days) b e ‘ jjfll"

the

mean

mid

after the Comet is in Perihelia at P, will give th e ^mean Motion or Area P R Q_S for anyComet Qjn its Orbit. In order to this we r® 3the Time ascertained from Observation whenwas in Perihelia at P, and also the Perihelia 11 , ]ipti c ■,SP from the Sun ; as also the Place in the F c | jj)C^she fame Time, the Position of its Nodes, 311 .. ^nation of its Orbit : All which Particulars fo r $!_mets the Industry of the great Astronomer of s ‘ J;/Phas supplied, viz. Dr. Hallcy, in his Cornedwhich I have transcribed, and added thereto 11T hings for the last Comet, as they were d et . p s 0by the Reverend Mr. Beits, from the Obscr va 0 i\Mr. Professor Bliss of Oxford , at the Observatory 1

Right Hon. the Earl of Macdesfield , at Sb cr ,Oxferdjhire. n A fL

17. From the Place of the Comet Q_draW *4 {0 tlpendicular to the Axis ; and let a b be a'l a,1 » el !jiCurve in the Point Q_, and B Q_drawn p cr P cJ ^ c hkthereto; then by the Nature of the Parabola piA B r S R, the Semi-Latus Redium. And p u so ffgiven Area P Q_S -- a, and A Q_= x, wehr =3 a. or -f -12 et ■, which Cubic