MODERN COSMOGONIES By the Same Author A POPULAR HISTORY OF ASTRONOMY DURING THE NINETEENTH CENTURY FOURTH EDITION. DEMY 8VO., CLOTH, ILLUSTRATED PRICE 15s. NET PROBLEMS IN ASTROPHYSICS DEMY 8VO., CLOTH, ILLUSTRATED PRICE 20s. NET THE SYSTEM OF THE STARS SECOND EDITION DEMY 8VO., CLOTH, ILLUSTRATED PRICE 20s. NET A. & C. Black · Soho Square · London, W. '_The world's a prophecy of worlds to come._'--Young MODERN COSMOGONIES BY AGNES M. CLERKE HON. MEM. R.A.S. AUTHOR OF 'A POPULAR HISTORY OF ASTRONOMY DURING THE NINETEENTH CENTURY,' 'THE SYSTEM OF THE STARS,' 'PROBLEMS IN ASTROPHYSICS,' AND OTHER WORKS LONDON ADAM AND CHARLES BLACK 1905 PREFACE Of the sixteen chapters constituting this little work, thirteen have been published as a series, begun in _Knowledge_ and continued in _Knowledge and Illustrated Scientific News_, and to the proprietors of those journals, for their courteous permission to reprint them, I offer my sincere thanks. Three additional chapters, equivalent to, though not identical with, those that now appear, formed an integral part of the original plan of the book, now presented to the public in the hope that it will enable general readers to follow, with the profound interest it should inspire, the course of modern inquiries regarding the origin of the world. Their advance is by no means smooth or facile. Many difficulties and perplexities are encountered in the attempt to get back towards the beginning of things. Some of the old tracks, too, have been torn up by the pioneers of twentieth century science, and the process of constructing new ones, which shall lead further into the unknown fore-time, is slow and laborious. But the rail-head in the desert is a peculiarly suggestive place of pilgrimage, and several such outlying posts and temporary halting-places are more or less vaguely localized in the following pages. London, _November, 16, 1905_. CONTENTS CHAPTER PAGE I. FROM THALES TO KANT 1 II. THE NEBULAR HYPOTHESIS 21 III. CRITICISMS OF THE NEBULAR HYPOTHESIS 39 IV. THE NEBULAR HYPOTHESIS VARIED AND IMPROVED 60 V. TIDAL FRICTION AS AN AGENT IN COSMOGONY 83 VI. THE FISSION OF ROTATING GLOBES 100 VII. WORLD-BUILDING OUT OF METEORITES 118 VIII. COSMOGONY IN THE TWENTIETH CENTURY 135 IX. PROTYLE: WHAT IS IT? 150 X. UNIVERSAL FORCES 166 XI. THE INEVITABLE ETHER 183 XII. THE FORMS OF NEBULÆ 199 XIII. THE PROCESSION OF SUNS 216 XIV. OUR OWN SYSTEM 232 XV. REMNANTS AND SURVIVALS 250 XVI. LIFE AS THE OUTCOME 265