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
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
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