Astronomical Discovery

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ASTRONOMICAL DISCOVERY




[Illustration: ASTRONOMERS ROYAL.]




  ASTRONOMICAL
  DISCOVERY


  BY
  HERBERT HALL TURNER, D.Sc., F.R.S.

  SAVILIAN PROFESSOR OF ASTRONOMY IN THE
  UNIVERSITY OF OXFORD


  _WITH PLATES_


  LONDON
  EDWARD ARNOLD
  41 & 43 MADDOX STREET, W.
  1904

  (All rights reserved)



  TO

  EDWARD EMERSON BARNARD
  ASTRONOMICAL DISCOVERER

  THESE PAGES ARE INSCRIBED IN MEMORY OF
  NEVER-TO-BE-FORGOTTEN DAYS SPENT WITH HIM AT THE
  YERKES OBSERVATORY OF
  THE UNIVERSITY OF CHICAGO




PREFACE


The aim of the following pages is to illustrate, by the study of a few
examples chosen almost at random, the variety in character of astronomical
discoveries. An attempt has indeed been made to arrange the half-dozen
examples, once selected, into a rough sequence according to the amount of
"chance" associated with the discovery, though from this point of view
Chapter IV. should come first; but I do not lay much stress upon it. There
is undoubtedly an element of "luck" in most discoveries. "The biggest
strokes are all luck," writes a brother astronomer who had done me the
honour to glance at a few pages, "but a man must not drop his catches.
Have you ever read Montaigne's essay 'Of Glory'? It is worth reading.
Change war and glory to discovery and it is exactly the same theme. If you
are looking for a motto you will find a score in it." Indeed even in cases
such as those in Chapters V. and VI., where a discovery is made by turning
over a heap of rubbish--declared such by experts and abandoned
accordingly--we instinctively feel that the finding of something valuable
was especially "fortunate." We should scarcely recommend such waste
material as the best hunting ground for gems.

The chapters correspond approximately to a series of six lectures
delivered at the University of Chicago in August 1904, at the hospitable
invitation of President Harper. They afforded me the opportunity of seeing
something of this wonderful University, only a dozen years old and yet so
amazingly vigorous; and especially of its observatory (the Yerkes
observatory, situated eighty miles away on Lake Geneva), which is only
eight years old and yet has taken its place in the foremost rank. For
these opportunities I venture here to put on record my grateful thanks.

In a portion of the first chapter it will be obvious that I am indebted to
Miss Clerke's "History of Astronomy in the Nineteenth Century"; in the
second to Professor R. A. Sampson's Memoir on the Adams MSS.; in the third
to Rigaud's "Life of Bradley." There are other debts which I hope are duly
acknowledged in the text. My grateful thanks are due to Mr. F. A. Bellamy
for the care with which he has read the proofs; and I am indebted for
permission to publish illustrations to the Royal Astronomical Society, the
Astronomer Royal, the editors of _The Observatory_, the Cambridge
University Press, the Harvard College Observatory, the Yerkes Observatory,
and the living representatives of two portraits.

H. H. TURNER.

  UNIVERSITY OBSERVATORY, OXFORD,
  _November 9, 1904_.




CONTENTS


                                                                    PAGE
  CHAPTER I
      URANUS AND EROS                                                  1

  CHAPTER II
      THE DISCOVERY OF NEPTUNE                                        38

  CHAPTER III
      BRADLEY'S DISCOVERIES OF THE ABERRATION OF LIGHT AND OF THE
      NUTATION OF THE EARTH'S AXIS                                    86

  CHAPTER IV
      ACCIDENTAL DISCOVERIES                                         121

  CHAPTER V
      SCHWABE AND THE SUN-SPOT PERIOD                                155

  CHAPTER VI
      THE VARIATION OF LATITUDE                                      177

  INDEX                                                              221




LIST OF PLATES


  PLATE

     I. PORTRAIT OF J. C. ADAMS                        _To face page_ 22

    II. PORTRAIT OF A. GRAHAM                               "    "    22

   III. PORTRAIT OF U. J. LE VERRIER                        "    "    60

    IV. PORTRAIT OF J. G. GALLE                             "    "    60

     V. CORNER OF THE BERLIN MAP BY THE USE OF WHICH
        GALLE FOUND NEPTUNE                                 "    "    82

    VI. ASTRONOMERS ROYAL                                 _Frontispiece_

   VII. GREAT COMET OF NOV. 7, 1882                   _To face page_ 122

  VIII. THE OXFORD NEW STAR                                "    "    142

    IX. NEBULOSITY ROUND NOVA PERSEI                       "    "    146

     X. SUN-SPOTS AT GREENWICH, FEB. 18 AND 19, 1894       "    "    158

    XI. SUN-SPOTS AT GREENWICH, FEB. 20 AND 21, 1894       "    "    162

   XII.