[Illustration: ARCTIC SLEDGE-JOURNEY.] THE SEA AND ITS LIVING WONDERS A POPULAR ACCOUNT OF THE MARVELS OF THE DEEP AND OF THE PROGRESS OF MARITIME DISCOVERY FROM THE EARLIEST AGES TO THE PRESENT TIME BY DR. G. HARTWIG AUTHOR OF "THE TROPICAL WORLD" "THE HARMONIES OF NATURE" "THE POLAR WORLD" AND "THE SUBTERRANEAN WORLD" SEVENTH EDITION _WITH NUMEROUS WOODCUTS AND PLATES_ LONDON LONGMANS, GREEN, AND CO. AND NEW YORK: 15 EAST 16^{th} STREET 1892 NOTICE _The right of translation into French is reserved by the Author. All necessary steps for securing the Copyright have been taken._ PREFACE TO THE THIRD AND FOURTH EDITIONS. Nothing can be more agreeable to an author anxious to merit the suffrages of the public, than the opportunity afforded him, by a new edition, of correcting past errors or adding improvements to his work. Should any one of my readers think it worth his while to compare 'The Sea,' such as it now is, with what it formerly was, I have no doubt he will do me the justice to say that I have conscientiously striven to deserve his approbation. Two new chapters--one on Marine Constructions, the other on Marine Caves--have been added; those on the Molluscs and Cœlenterata (Jelly-fishes, Polyps) almost entirely re-written; and those on Fishes, Crustaceans, Microscopic Animals, the Geographical Distribution of Marine Life, and the Phosphorescence of the Sea, considerably enlarged; not to mention a number of minor improvements dispersed throughout the volume. Great attention has also been paid to the Illustrations, many of questionable value having been omitted in the present edition, to make room for a number of others, which will be found of great use for the better understanding of the text. In one word, I have done my best to raise my work to the standard of the actual state of science, and to render it, as far as my humble abilities go, a complete epitome of all that the _general_ reader _cares_ to know about the marvels of the deep. G. Hartwig. Salon Villas, Ludwigsburg: _June 30, 1873_. PREFACE TO THE FIRST TWO EDITIONS. For years my daily walks have been upon the beach, and I have learnt to love the ocean as the Swiss mountaineer loves his native Alps, or the Highlander the heath-covered hills of Caledonia. May these feelings have imparted some warmth to the following pages, and serve to render the reader more indulgent to their faults! G. Hartwig. Göttingen: _July 17, 1860_. CONTENTS. PART I. THE PHYSICAL GEOGRAPHY OF THE SEA. CHAPTER I. THE MAGNITUDE OF THE SEA.