| PREFACE |
iii - viii.
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| INTRODUCTION | |
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PART I.
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CHAPTER I.
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| General notions. Apparent and real motions. Shape and size of the Earth. The horizon and its dip. The atmosphere. Refraction. Twilight. 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 | |
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CHAPTER II.
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| Terminology and elementary geometrical conceptions and relations. Terminology relating to the globe of the Earth - to the celestial sphere. Celestial perspective | |
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CHAPTER III.
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| 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 Benzenberg. Of compound instruments with co-ordinate circles. The equatorial, altitude, and azimuth instrument. Theodolite. Of the sextant and reflecting circle. Principle of repetition. Of micrometers. Parallel wire micrometer. Principle of the duplication of images. The heliometer. Double refracting eye-piece. Variable prism micrometer. Of the position micrometer | |
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CHAPTER IV
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OF GEOGRAPHY. |
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| 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. Projections of the sphere. Measurement of heights by the barometer | |
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CHAPTER V.
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OF URANOGRAPHY. |
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| Construction of celestial maps and globes by observations of right ascension 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 corrections | |
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CHAPTER VI.
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OF THE SUN'S MOTION. |
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| 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. Mean and true longitudes of the Sun. Equation of the centre. Sidereal, tropical, and anomalistic years. Physical constitution of the Sun. Its spots. Faculæ. Probable nature and cause of the spots. Atmosphere of the Sun. Its supposed clouds. Temperature at its surface. Its expenditure of heat. Terrestrial effects of solar radation | |
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CHAPTER VII.
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| Of the Moon. Its sidereal period. Its apparent diameter. Its parallax, 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. Of eclipses more particularly. Their phenomena. Their periodical recurrence. Physical constitution of the Moon. Its mountains and other superficial features. Indications of former volcanic activity. Its atmosphere. Climate. Radiation of heat from its surface. Rotation on its own axis. Libration. Appearance of the Earth from it | |
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CHAPTER VIII.
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| 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 | |
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CHAPTER IX.
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OF THE SOLAR SYSTEM. |
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| Apparent motions of the planets. Their stations and retrogradations. The Sun their natural centre 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 ultra-zodiacal planets. Physical peculiarities observable in each of the planets | |
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CHAPTER X.
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OF THE SATELLITES. |
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| 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 means. Satellites of Saturn - of Uranus - of Neptune | |
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CHAPTER XI.
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OF COMETS. |
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| Great number of recorded comets. The number of those unrecorded probably much greater. General description of a comet. Comets without 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 - Biela's - Faye's - Lexell's - De Vico's - Brorsen's - Peter's. Great comet of 1843. Its probable identity with several older comets. Great interest at present attached to cometary astronomy, and its reasons. Remarks on cometary orbits in general | |
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PART II.
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OF THE PLANETARY PERTURBATIONS. |
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CHAPTER XII.
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| Subject propounded. Problem of three bodies. Superposition of small motions. Estimation of the disturbing force. Its geometrical representation. Numerical estimation in particular cases. Resolution into rectangular components. Radial, transversal, and orthogonal disturbing forces. Normal and tangential. Their characteristic effects. Effects of the orthogonal force. Motion of the nodes. Conditions of their advance and recess. Cases of an exterior planet disturbed by an interior. The reverse case. In every case the node of the disturbed orbit recedes on the plane of the disturbing on an average. Combined effect of many such disturbances. Motion of the Moon's nodes. Change of inclination. Conditions of its increase and diminution. Average effect in a whole revolution. Compensation in a complete revolution of the nodes. Lagrange's theorem of the stability of the inclinations of the planetary orbits. Change of obliquity of the ecliptic. Precession of the equinoxes explained. Nutation. Principle of forced vibrations | |
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CHAPTER XIII.
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THEORY OF THE AXES, PERIHELIA, AND EXCENTRICITIES. |
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| Variation of elements in general. Distinction between periodic and secular variations. Geometrical expression of tangential and normal forces. Variation of the Major Axis produced only by the tangential force. Lagrange's theorem of the conservation of the mean distances and periods. Theory of the Perihelia and excentricities. Geometrical representation of their momentary variations. Estimation of the disturbing forces in nearly circular orbits. Application to the case of the Moon. Theory of the lunar apsides and excentricity. Experimental illustration. Application of the foregoing principles to the Planetary theory. Compensation in orbits very nearly circular. Effects of ellipticity. General results. Lagrange's theorem of the stability of the excentricities | |
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CHAPTER XIV.
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| Of the inequalities independent of the excentricities. The Moon's variation and parallactic inequality. Analogous planetary inequalities. Three cases of Planetary perturbation distinguished. Of inequalities dependent on the excentricites. Long inequality of Jupiter and Saturn. Law of reciprocity between the periodical variations of the elements of both planets. Long inequality of the Earth and Venus. Variation of the epoch. Inequalities incident on the epoch affecting the mean motion. Interpretation of the constant part of these inequalities. Annual equation of the Moon. Her secular acceleration. Lunar inequalities due to the action of Venus. Effect of the spheroidal figure of the Earth and other planets on the motions of their satellites. Of the tides. Masses of disturbing bodies deducible from the perturbations they produce. Mass of the Moon, and of Jupiter's satellites, how ascertained. Perturbations of Uranus resulting in the discovery of Neptune | |
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PART III.
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OF SIDEREAL ASTRONOMY. |
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CHAPTER XV.
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| Of the fixed stars. Their classification by magnitudes. Photometric scale of magnitudes. Conventional or vulgar scale. Photometric comparison of stars. Distribution of stars over the heavens. Of the Milky Way or galaxy. Its supposed form that of a flat stratum partially subdivided. Its visible course among the constellations. Its Internal structure. Its apparently indefinite extent in certain directions. Of the distance of the fixed stars. Their annual parallax. Parallactic unit of sidereal distance. Effect of parallax analogous to that of aberration. How distinguished from it. Detection of parallax by meridional observations. Henderson's application to a centauri. By differential observations. Discoveries of Bessel and Struve. List of stars in which parallax has been detected. Of the real magnitudes of the stars. Comparison of their lights with that of the Sun | |
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CHAPTER XVI.
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| Variable and periodical stars. List of those already known. Irregularities in their periods and lustre when brightest. Irregular and temporary stars. Ancient Chinese records of several. Missing stars. Double stars. Their classification. Specimens of each class. Binary systems. Revolution round each other. Describe elliptic orbits under the Newtonian law of gravity. Elements of orbits of several. Actual dimensions of their orbits. Coloured double stars. Phænomenon of complementary colours. Sanguine stars. Proper motion of the stars. Partly accounted for by a real motion of the Sun. Situation of the solar apex. Agreement of southern and northern stars in giving the same result. Principles on which the investigation of the solar motion depends. Absolute velocity of the Sun's motion. Supposed revolution of the whole sidereal system round a common centre. Systematic parallax and aberration. Effect of the motion of light in altering the apparent period of a binary star | |
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CHAPTER XVII.
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OF CLUSTERS OF STARS AND NEBULÆ. |
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| Of clustering groups of stars. Globular clusters. Their stability dynamically possible. List of the most remarkable. Classification of nebulæ and clusters. Their distribution over the heavens. Irregular clusters. Resolvability of nebulæ. Theory of the formation of clusters by nebulous subsidence. Of elliptic nebulæ. That of Andromeda. Annular and planetary nebulæ. Double nebulæ. Nebulous stars. Connection of nebulæ with double stars. Insulated nebulæ of forms not wholly irregular. Of amorphous nebulæ. Their law of distribution marks them as outliers of the galaxy. Nebulæ and nebulous group of Orion - of Argo - of Sagittarius - of Cygnus. The Magellanic clouds. Singular nebula in the greater of them. The zodiacal light. Shooting stars | |
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PART IV.
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OF THE ACCOUNT OF TIME. |
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CHAPTER XVIII.
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| Natural units of time. Relation of the sidereal to the solar day affected by precession. Incommensurability of the day and year. Its inconvenience. How obviated. The Julian Calendar. Irregularities at its first introduction. Reformed by Augustus. Gregorian reformation. Solar and lunar cycles. Indiction. Julian period. Table of Chronological eras. Rules for calculating the days elapsed between given Dates. Equinoctial time. | |
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APPENDIX.
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| I. Lists of Northern and Southern Stars, with their approximate Magnitudes, on the Vulgar and Photometric Scales | |
| II. Synoptic Table of the Elements of the Planetary System | |
| III. Synoptic Table of the Elements of the Orbits of the Satellites, so far as they are known | |
| IV. Elements of Periodical Comets at their last Appearance | |
| INDEX | |