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 125 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 143 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 166 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 194 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 216 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 227 CHAPTER VII PLANETS AND SATELLITES