tag="{http://www.w3.org/1999/xhtml}a">CHAPTER VI

INSTRUMENTAL ADVANCES

Two Principles of Telescopic Construction—Early Reflectors—Three Varieties—Herschel's Specula—High Magnifying Powers—Invention of the Achromatic Lens—Guinand's Optical Glass—The Great Rosse Reflector—Its Disclosures—Mounting of Telescopes—Astronomical Circles—Personal Equation

PART II

RECENT PROGRESS OF ASTRONOMY

CHAPTER I

FOUNDATION OF ASTRONOMICAL PHYSICS

Schwabe's Discovery of a Decennial Sun-spot Period—Coincidence with Period of Magnetic Disturbance—Sun-spots and Weather—Spectrum Analysis—Preliminary Inquiries—Fraunhofer Lines—Kirchhoff's Principle—Anticipations—Elementary Principles of Spectrum Analysis—Unity of Nature

CHAPTER II

SOLAR OBSERVATIONS AND THEORIES

Black Openings in Spots—Carrington's Observations—Rotation of the Sun—Kirchhoff's Theory of the Solar Constitution—Faye's Views—Solar Photography—Kew Observations—Spectroscopic Method—Cyclonic Theory of Sun-spots—Volcanic Hypothesis—A Solar Outburst—Sun-spot Periodicity—Planetary Influence—Structure of the Photosphere

CHAPTER III

RECENT SOLAR ECLIPSES

Expeditions to Spain—Great Indian Eclipse—New Method of Viewing Prominences—Total Eclipse Visible in North America—Spectrum of the Corona—Eclipse of 1870—Young's Reversing Layer—Eclipse of 1871—Corona of 1878—Varying Coronal Types—Egyptian Eclipse—Daylight Coronal Photography—Observations at Caroline Island—Photographs of Corona in 1886 and 1889—Eclipses of 1896, 1898, 1900, and 1901—Mechanical Theory of Corona—Electro-Magnetic Theories—Nature of Corona

CHAPTER IV

SOLAR SPECTROSCOPY

Chemistry of Prominences—Study of their Forms—Two Classes—Photographs and Spectrographs of Prominences—Their Distribution—Structure of the Chromosphere—Spectroscopic Measurement of Radial Movements—Spectroscopic Determination of Solar Rotation—Velocities of Transport in the Sun—Lockyer's Theory of Dissociation—Solar Constituents—Oxygen Absorption in Solar Spectrum

CHAPTER V

TEMPERATURE OF THE SUN

Thermal Power of the Sun—Radiation and Temperature—Estimates of Solar Temperature—Rosetti's and Wilson's Results—Zöllner's Method—Langley's Experiment at Pittsburg—The Sun's Atmosphere—Langley's Bolometric Researches—Selective Absorption by our Air—The Solar Constant

CHAPTER VI

THE SUN'S DISTANCE

Difficulty of the Problem—Oppositions of Mars—Transits of Venus—Lunar Disturbance—Velocity of Light—Transit of 1874—Inconclusive Result—Opposition of Mars in 1877—Measurements of Minor Planets—Transit of 1882—Newcomb's Determination of the Velocity of Light—Combined Result

CHAPTER VII

PLANETS AND SATELLITES

Schröter's Life and Work—Luminous Appearances during Transits of Mercury—Mountains of Mercury—Intra-Mercurian Planets—Schiaparelli's Results for the Rotation of Mercury and Venus—Illusory Satellite—Mountains and Atmosphere of Venus—Ashen Light—Solidity of the Earth—Variation of Latitude—Secular Changes of Climate—Figure of the Globe—Study of the Moon's Surface—Lunar Atmosphere—New Craters—Thermal Energy of Moonlight—Tidal Friction

CHAPTER VIII

PLANETS AND SATELLITES—(continued)

Analogy between Mars and the Earth—Martian Snowcaps, Seas, and Continents—Climate and Atmosphere—Schiaparelli's Canals—Discovery of Two Martian Satellites—Photographic Detection of Minor Planets—Orbit of Eros—Distribution of the Minor Planets—Their Collective Mass and Estimated Diameters—Condition of Jupiter—His Spectrum—Transits of his Satellites—Discovery of a Fifth Satellite—The Great Red Spot—Constitution of Saturn's Rings—Period of Rotation of the Planet—Variability of Japetus—Equatorial Markings on Uranus—His Spectrum—Rotation of Neptune—Trans-Neptunian Planets

CHAPTER IX

THEORIES OF PLANETARY EVOLUTION

Origin of the World according to Kant—Laplace's Nebular Hypothesis—Maintenance of the Sun's Heat—Meteoric Hypothesis—Radiation as an Effect of Contraction—Regenerative Theory—Faye's Scheme of Planetary Development—Origin of the Moon—Effects of Tidal

CHAPTER X

RECENT COMETS

Donati's Comet—The Earth again Involved in a Comet's Tail—Comets of the August and November Meteors—Star Showers—Comets and Meteors—Biela's Comet and the Andromedes—Holmes's Comet—Deflection of the Leonids—Orbits of Meteorites—Meteors with Stationary Radiants—Spectroscopic Analysis of Cometary Light—Comet of 1901—Coggia's Comet

CHAPTER XI

RECENT COMETS—(continued)

Forms of Comets' Tails—Electrical Repulsion—Brédikhine's Three Types—Great Southern Comet—Supposed Previous Appearances—Tebbutt's Comet and the Comet of 1807—Successful Photographs—Schaeberle's Comet—Comet Wells—Sodium Blaze in Spectrum—Great Comet of 1882—Transit across the Sun—Relation to Comets of 1843 and 1880—Cometary Systems—Spectral Changes in Comet of 1882—Brooks's Comet of 1889—Swift's Comet of 1892—Origin of Comets