GREAT ASTRONOMERS by SIR ROBERT S. BALL D.Sc. LL.D. F.R.S. Lowndean Professor of Astronomy and Geometry in the University of Cambridge Author of "In Starry Realms" "In the High Heavens" etc. WITH NUMEROUS ILLUSTRATIONS [PLATE: GREENWICH OBSERVATORY.] PREFACE. It has been my object in these pages to present the life of each astronomer in such detail as to enable the reader to realise in some degree the man's character and surroundings; and I have endeavoured to indicate as clearly as circumstances would permit the main features of the discoveries by which he has become known. There are many types of astronomers--from the stargazer who merely watches the heavens, to the abstract mathematician who merely works at his desk; it has, consequently, been necessary in the case of some lives to adopt a very different treatment from that which seemed suitable for others. While the work was in progress, some of the sketches appeared in "Good Words." The chapter on Brinkley has been chiefly derived from an article on the "History of Dunsink Observatory," which was published on the occasion of the tercentenary celebration of the University of Dublin in 1892, and the life of Sir William Rowan Hamilton is taken, with a few alterations and omissions, from an article contributed to the "Quarterly Review" on Graves' life of the great mathematician. The remaining chapters now appear for the first time. For many of the facts contained in the sketch of the late Professor Adams, I am indebted to the obituary notice written by my friend Dr. J. W. L. Glaisher, for the Royal Astronomical Society; while with regard to the late Sir George Airy, I have a similar acknowledgment to make to Professor H. H. Turner. To my friend Dr. Arthur A. Rambaut I owe my hearty thanks for his kindness in aiding me in the revision of the work. R.S.B. The Observatory, Cambridge. October, 1895 CONTENTS. INTRODUCTION. PTOLEMY. COPERNICUS. TYCHO BRAHE. GALILEO. KEPLER. ISAAC NEWTON. FLAMSTEED. HALLEY. BRADLEY. WILLIAM HERSCHEL. LAPLACE. BRINKLEY. JOHN HERSCHEL. THE EARL OF ROSSE. AIRY. HAMILTON. LE VERRIER. ADAMS. LIST OF ILLUSTRATIONS. THE OBSERVATORY, GREENWICH. PTOLEMY. PTOLEMY'S PLANETARY SCHEME. PTOLEMY'S THEORY OF THE MOVEMENT OF MARS. THORN, FROM AN OLD PRINT. COPERNICUS. FRAUENBURG, FROM AN OLD PRINT. EXPLANATION OF PLANETARY MOVEMENTS. TYCHO BRAHE. TYCHO'S CROSS STAFF. TYCHO'S "NEW STAR" SEXTANT OF 1572. TYCHO'S TRIGONIC SEXTANT. TYCHO'S ASTRONOMIC SEXTANT. TYCHO'S EQUATORIAL ARMILLARY. THE GREAT AUGSBURG QUADRANT. TYCHO'S "NEW SCHEME OF THE TERRESTRIAL SYSTEM," 1577. URANIBORG AND ITS GROUNDS. GROUND-PLAN OF THE OBSERVATORY. THE OBSERVATORY OF URANIBORG, ISLAND OF HVEN. EFFIGY ON TYCHO'S TOMB AT PRAGUE. By Permission of Messrs. A. & C. Black. TYCHO'S MURAL QUADRANT, URANIBORG. GALILEO'S PENDULUM. GALILEO. THE VILLA ARCETRI. FACSIMILE SKETCH OF LUNAR SURFACE BY GALILEO. CREST OF GALILEO'S FAMILY.