Outlines of astronomy - sir John Frederick W. Herschel (1st bart.) - Google Books

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LIST OF PLATES.

PLATE I. Frontispiece.

Fig. 1. Faculæ of the Sun.
Fig. 2. Spots on ditto.
Fig. 3. Appearance of ditto in a total Eclipse, showing the

red flames.
Fig. 4. 5. Spots as seen by Mr. Dawes.
PLATE II. Fig. 1. Messier's 13th Nebula resolved into Stars.

Fig. 2. The Comet of 1819.

Fig. 3. The Nebula in Andromeda. Plate III. Fig. 1. Mars as seen August 16th, 1830.

Fig. 2. Jupiter as seen September 23rd, 1832.

Fig. 3. Saturn, showing the interior rings and belts. PLATE IV. Fig. 1. The great Nebula in Orion.

Fig. 2. The great Nebula in Argo. Plate V. Fig. 1. Nebula (30 Doradûs) in the Nubecula Major. Fig. 2. Lunar Volcano, as shown by a 20 feet reflecting Te

lescope, aperture 18 inches. PLATE VI. Fig. 1. Various Appearances of Halley's Comet at its last

Apparition.
Fig. 2. Double Comet of Biela, as seen on its last return.
Fig. 3. Messier's 51st Nebula as shown by Lord Rosse's

great Reflector. Plate A. Figures illustrative of the Perturbations of Uranus by Nep

tune.

CONTENTS.

PREFACE
INTRODUCTION

:

- Page üii—viü.

1

General notions. Apparent and real motions. Shape and size of the

Earth. The horizon and its dip. The atmosphere. Refraction. Twi-

light. Appearances resulting from diurnal motion. From change of

station in general. Parallactic motions. Terrestrial parallax. That

of the stars insensible. First step towards forming an idea of the

distance of the stars. Copernican view of the Earth's motion. Relative

motion. Motions partly real, partly apparent. Geocentric astronomy,

or ideal reference of phænomena to the Earth's centre as a common

conventional station

Terminology and elementary geometrical conceptions and relations. Ter-

minology relating to the globe of the Earth — to the celestial sphere.

Celestial perspective

CHAPTER IIT.

Of the nature of astronomical instruments and observations in general.

Of sidereal and solar time. Of the measurements of time. Clocks,

chronometers. Of astronomical measurements. Principle of telescopic

sights to increase the accuracy of pointing. Simplest application of

this principle. The transit instrument. Of the measurement of

angular intervals. Methods of increasing the accuracy of reading.

The vernier. The microscope. Of the mural circle. The Meridian

circle. Fixation of polar and horizontal points. The level, plumb-

line, artificial horizon. Principle of collimation. Collimators of

Rittenhouse, Kater, and Bohnenberger. Of compound instruments with

co-ordinate circles. The equatorial, altitude, and azimuth instrument.

Theodolite. Of the sextant and reflecting circle. Principle of re-

petition. Of micrometers. Parallel wire micrometer. Principle of the

duplication of images. The heliometer. Double refracting eye-piece.

Variable prism micrometer. Of the position micrometer. Illumination

of wires. Solar telescope and eye-piece. Helioscopy. Collimation of

large reflectors

Of the figure of the Earth. Its exact dimensions. Its form that of

equilibrium modified by centrifugal force. Variation of gravity on its

surface. Statical and dynamical measures of gravity. The pendulum.

Gravity to a spheroid. Other effects of the Earth's rotation. Trade

winds. Determination of geographical positions - of latitudes — of

longitudes. Conduct of a trigonometrical survey. Of maps. Projec-

tions of the sphere. Measurement of heights by the barometer

OF URANOGRAPHY.

Construction of celestial maps and globes by observations of right ascen-

sion and declination. Celestial objects distinguished into fixed and

erratic. Of the constellations. Natural regions in the heavens. The

Milky Way. The Zodiac. Of the ecliptic. Celestial latitudes and

longitudes. Precession of the equinoxes. Nutation. Aberration

Refraction. Parallax. Summary view of the uranographical cor-

OF THE SUN'S MOTION.

Apparent motion of the Sun not uniform. Its apparent diameter also

variable, Variation of its distance concluded. Its apparent orbit an

ellipse about the focus. Law of the angular velocity. Equable

description of areas. Parallax of the Sun. Its distance and magnitude.

Copernican explanation of the Sun's apparent motion. Parallelism of

the Earth's axis. The seasons. Heat received from the Sun in

different parts of the orbit. Effect of excentricity of the orbit and

position of its axis on climate. Mean and true longitudes of the Sun.

Equation of the center. Sidereal, tropical, and anomalistic years.

Physical constitution of the Sun. Its spots. Faculæ. Probable na.

ture and cause of the spots. Recent discoveries of Mr. Dawes. Rota-

tion of the Sun on its axis. Its atmosphere. Supposed clouds. Perio-

dical recurrence of a more and less spotted state of its surface. 219

Of the Moon. Its sidereal period. Its apparent diameter. Its parallax,
eclipses more particularly. Their phænomena. Their periodical recur-

distance, and real diameter. First approximation to its orbit. An

ellipse about the Earth in the focus. Its excentricity and inclination.

Motion of its nodes and apsides. Of occultations and solar eclipses

generally. Limits within which they are possible. They prove the

Moon to be an opaque solid. Its light derived from the Sun. Its

phases. Synodic revolution or lunar month. Harvest Moon. Of

rence. Physical constitution of the Moon. Its mountains and other

superficial features. Indications of former volcanic activity. Its atmo-

sphere. Climate. Radiation of heat from its surface. Rotation on

its own axis. Libration. Appearance of the Earth from it. Probable

elongation of the Moon's figure in the direction of the Earth. Its

habitability not possible

Of terrestrial gravity. Of the law of universal gravitation. Paths of

projectiles, apparent, real. The Moon retained in her orbit by gravity.

Its law of diminution. Laws of elliptic motion. Orbit of the Earth

round the Sun in accordance with these laws. Masses of the Earth

and Sun compared. Density of the Sun. Force of gravity at its

surface. Disturbing effect of the Sun on the Moon's motion 290

OF THE SOLAR SYSTEM.

Apparent motions of the planets. The stations and retrogradations.

The Sun their natural center of motion. Inferior planets. Their

phases, periods, etc. Dimensions and form of their orbits. Transits

across the Sun. Superior planets. Their distances, periods, etc.

Kepler's laws and their interpretation. Elliptic elements of a planet's

orbit. Its heliocentric and geocentric place. Empirical law of planetary

distances ; violated in the case of Neptune. The asteroids. Physical

peculiarities observable in each of the planets

OF THE SATELLITES.

Of the Moon, as a satellite of the Earth. General proximity of satellites

to their primaries, and consequent subordination of their motions.

Masses of the primaries concluded from the periods of their satellites.

Maintenance of Kepler's laws in the secondary systems. Of Jupiter's

satellites. Their eclipses, etc. Velocity of light discovered by their

Satellites of Saturn- of Uranus - of Neptune

Great number of recorded comets. The number of those unrecorded

probably much greater. General description of a comet. Comets with-

out tails, or with more than one. Their extreme tenuity. Their

probable structure. Motions conformable to the law of gravity.

Actual dimensions of comets. Periodical return of several. Halley's

comet. Other ancient comets probably periodic. Encke's comet-

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