Comets Author:Charles P. Olivier Text extracted from opening pages of book: COMETS BY PROFESSOR OF ASTRONOMY AND DIRECTOR OF FLOWER OBSERVATORY, UNIVERSITY OF PENNSYLVANIA LONDON BAILLlfiRE, TINDALL AND COX S Henrietta Street, Covent Garden, W. C. 2 1030 ALL RIGHTS RESERVED, 1930 PRINTED IN AMERICA TO MY WIFE MARY FRANCES FENDER OLIVIER THIS BOOK IS AFFECTIONATELY DEDICATED PRE... more »FACE The study of meteoric astronomy, es pecially in its theoretical aspects, gradually drew the author's attention to the need of a closer study of comets. This in turn led back to the origins of all the minor bodies of the Solar System and to similarities that exist be tween them. The appearance of the impor tant book by T. C. Chamberlin, The Two Solar Families, also stimulated this interest. Further no recent book on comets, which covers the theoretical side, is available in the English language. Consequently it seemed that a book of moderate size, which would cover briefly the history of the subject and the present theories of origin, constitution, changes, and dissolution of comets, would be useful to the astronomer who does not special ize in the subject, as well as to the average intelligent reader. It is the author's aim to fill these requirements, leaving out entirely any mathematical discussions. This book docs not claim to cover the whole field; only selected comets are described. Also important work by some investigators is viii PREFACE perforce omitted. The book is intended as a sequel to older books on the same subject, such as for instance Chambers' The Story of the Comets, rather than to replace them. It is further intended as a direct sequel to the author's book Meteors, as new information and discoveries have permitted a considerable extension of certain theories tentatively ad vanced in its closing chapters. Also the ties between comets and meteors are so numerous that some knowledge of the one is necessary to understand the phenomena connected with the other. The author desires to express his sincere appreciation to his colleague, Dr. S. G. Barton, for kindly reading and correcting the manu script, and for helpful criticism in its prepa ration. CHAS. P. OLIVIER. Flower Observatory University of Pennsylvania Upper Darby, Pa. February 27, 1930 CONTENTS CHAPTER I HISTORICAL REVIEW 1 CHAPTER II GENERAL STATEMENTS 16 CHAPTER III COMET GROUPS 37 CHAPTER IV COMET FAMILIES 47 CHAPTER 1 * THE TAILS OP COMETS i 58 CHAPTER \ T l THE SPECTRA OP COMETS 79 CHAPTER vl, r l II ALLEY' s COMET 94 CHAPTER VII\ l BIELA'S COMET 127 CHAPTER IX SEVERAL INTERESTING COMETS 149 CHAPTER X MOREHOUSE'S COMET 160 CHAPTER XI PON8-WlNNECKE* 8 COMET 168 CHAPTER XII COMET 1910a 178 X CONTENTS CHAPTER XIII COMETS AND METEOR STREAMS .......................... 185 CHAPTER XIV COLLISIONS OP COMETS WITH THE EARTH ................. 193 CHAPTER XV OK UGINS OP COMETS ..................................... 207 ir CHAPTER XVI CONCL BIONS ............................................. 220 APPENDIX .............................................. 233 INDEX .................................................. 241 CHAPTER I HISTORICAL REVIEW When beggars die, there are no comets seen, The Heavens themselves blaze forth the death of Princes. SHAKESPEARE, Julius Cupsar. Records of comets have come down , o us from remote antiquity. It is evident t u it the appearance of a brilliant p~^ unexpected comet in the sky must havj . caught the atten tion of men long before any permanent record of it could have been left ii'or posterity. But from the centuries preceding the Christian era on, numerous accounts of comets have survived, as well as some t heories advanced by Greek and Roman writers. The very word comet is derived directly from the Greek word Ko/ x 177-775, the long haired one. Many books give the Latin word coma, hair, as being the ancestor. Hence the comet was a hairy one. This name came quite naturally from the long tails so often accompanying the larger comets, and which attracted attention as being unique in form« less