THE ELEMENTS

OF

ASTRONOMY:

DESIGNED FOR THE USE OF STUDENTS IN
THE UNIVERSITY.

BY THE

REV. S. VINCE, A.M. F.R.S.

PLUMIAN PROFESSOR of ASTRONOMY and EXPERIMENTAL
PHILOSOPHY in the UNIVERSITY of CAMBRIDGE.

THIRD EDITION.

CAMBRIDGE:

Printed by J. Smith, Printer to the University:.

AND SOLD BY J. DEIGHTON, AND J. NICHOLSON, CAMBRIDGE;
AND W. H. LUNN, SOHO-SQUARE, LONDON.

Biblioths Rhen.-Traj. ✯

a. d.

Vir. Cl. G. Moll.

CONTENTS.

CHAP. I.

Definitions

II. On the Doctrine of the Sphere

III.

To determine the right Ascension, Decli-

nation, Latitude and Longitude of the

heavenly Bodies

IV. On the Equation of Time

V.

On the Length of the Year, the Precession

of the Equinoxes from Observation,

and Obliquity of the Ecliptic

VI. On Parallax

VII. On Refraction

VIII. On the System of the World

IX.

On Kepler's Discoveries

X. On the Motion of a Body in an Ellipse

about the Focus

XI. On the Opposition and Conjunction of the

Planets.

XII. On the mean Motion of the Planets

XIII. On the greatest Equation, Excentricity,

and Place of the Aphelia of the Orbits

of the Planets

XIV. On the Nodes and Inclinations of the

Orbits of the Planets

XV. On the apparent Motions and Phases of

the Planets

XVI. On the Moon's Motion from Observation,

and it's Phænomena

XVII. On the Rotation of the Sun and Planets

XVIII. On the Satellites

Page

1

13

41

47

58

65

78

83

90

94

106

110

XXI. On the Eclipses of the Sun and Moon

XXII. On the Transits of Mercury and Venus

XXIII. On Comets

XXV. On the Longitude of Places upon the Earth 283

XIX. On the Ring of Saturn

XX. On the Aberration of Light

SYSTEM

OF

ASTRONOMY.

CHAPTER I.

DEFINITIONS.

Art. 1. ASTRONOMY is that branch of Natural Philosophy which treats of the heavenly bodies. The determination of their magnitudes, distances, and the orbits which they describe, is called plane or pure Astronomy; and the investigation of the causes of their motions is called physical Astronomy. The former discoveries are made from observations on their apparent magnitudes and motions; and the latter from analogy, by applying those principles and laws of motion by which bodies on and near the earth are governed, to the other bodies in the system. The principles of plane Astronomy only are what we here propose to treat of, and we shall begin with the explanation of such terms as are the foundation of the science.

(2.) A great circle QRST of a sphere is one whose plane passes through it's center C; and a small circle BDHK is that whose plane does not pass through it's center.

A