Chapter 2

The work of William Herschel--His discovery of Uranus--His discovery that the stars are suns--His conception of the universe--His deduction that gravitation has caused the grouping of the heavenly bodies--The nebula, hypothesis,--Immanuel Kant's conception of the formation of the world--Defects in Kant's conception--Laplace's final solution of the problem--His explanation in detail--Change in the mental attitude of the world since Bruno--Asteroids and satellites--Discoveries of Olbersl--The mathematical calculations of Adams and Leverrier--The discovery of the inner ring of Saturn--Clerk Maxwell's paper on the stability of Saturn's rings--Helmholtz's conception of the action of tidal friction--Professor G. H. Darwin's estimate of the consequences of tidal action--Comets and meteors--Bredichin's cometary theory--The final solution of the structure of comets--Newcomb's estimate of the amount of cometary dust swept up daily by the earth--The fixed stars--John Herschel's studies of double stars--Fraunhofer's perfection of the refracting telescope--Bessel's measurement of the parallax of a star,--Henderson's measurements--Kirchhoff and Bunsen's perfection of the spectroscope--Wonderful revelations of the spectroscope--Lord Kelvin's estimate of the time that will be required for the earth to become completely cooled--Alvan Clark's discovery of the companion star of Sirius--The advent of the photographic film in astronomy--Dr. Huggins's studies of nebulae--Sir Norman Lockyer's "cosmogonic guess,"--Croll's pre-nebular theory.