State of Knowledge regarding the Stars in the Eighteenth Century-- Career of Sir William Herschel--Constitution of the Stellar System-- Double Stars--Herschel's Discovery of their Revolutions-- His Method of Star-gauging--Discoveries of Nebulæ--Theory of their Condensation into Stars--Summary of Results 9 CHAPTER II PROGRESS OF SIDEREAL ASTRONOMY Exact Astronomy in Germany--Career of Bessel--His _Fundamenta Astronomiæ_--Career of Fraunhofer--Parallaxes of Fixed Stars--Translation of the Solar System--Astronomy of the Invisible--Struve's Researches in Double Stars--Sir John Herschel's Exploration of the Heavens--Fifty Years' Progress 27 CHAPTER III PROGRESS OF KNOWLEDGE REGARDING THE SUN Early Views as to the Nature of Sun-spots--Wilson's Observations and Reasonings--Sir William Herschel's Theory of the Solar Constitution--Sir John Herschel's Trade-Wind Hypothesis--Baily's Beads--Total Solar Eclipse of 1842--Corona and Prominences--Eclipse of 1851 52 CHAPTER IV PLANETARY DISCOVERIES Bode's Law--Search for a Missing Planet--Its Discovery by Piazzi-- Further Discoveries of Minor Planets--Unexplained Disturbance of Uranus--Discovery of Neptune--Its Satellite--An Eighth Saturnian Moon--Saturn's Dusky Ring--The Uranian System 71 CHAPTER V COMETS Predicted Return of Halley's Comet--Career of Olbers--Acceleration of Encke's Comet--Biela's Comet--Its Duplication--Faye's Comet--Comet of 1811--Electrical Theory of Cometary Emanations--The Earth in a Comet's Tail--Second Return of Halley's Comet--Great Comet of 1843--Results to Knowledge 88 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 108 PART II _RECENT PROGRESS OF ASTRONOMY_ CHAPTER I FOUNDATION OF ASTRONOMICAL PHYSICS