The Sea

THE SEA THE SEA BY H. A. MAHMER ASSISTANT CHIEF, DIVISION OF TIDES AND CURRENTS I T NITED STATES COAST AND GEODETIC SURVEY AUTHOR OF THE TIDE ILLUSTRATED D. APPLETON AND COMPANY NEW YORK LONDON 1930 PREFACE UNDER the name of oceanography the science of the sea covers a broad field and deals with a great variety of inter esting matters more or less intimately related. And like other sciences nowadays, it is growing on the technical con tributions of specialists each engaged in cultivating in tensively some small patch of the vast domain. It is with the purpose of setting forth in nontechnical language the more salient features of our knowledge of the sea that this volume is written. No textbook on oceanog raphy is here attempted, the author hoping that a less formal treatment may more clearly bring out both the importance and the inherent interest of the subject. With this in mind, too, various matters connected with the sea are here considered which ordinarily fall outside the scope of formal treatises. The author is indebted to a number of persons for help and encouragement. He feels under special obligation to Capt. R. L. Faris, Assistant Director of the Coast and Geodetic Survey, for helpful criticism throughout the preparation of the book. Grateful acknowledgment is here made also to the editors of the Geographical Review and of the United States Naval I nst Hide Proceedings for their courtesy in permitting the author to republish here such portions of the work as have appeared in the pages of their journals. H. A. M. CONTENTS PAGE PREFACE v CHAPTER I. THE SEA OF ANCIENT TIMES 1 II. THE CROSSING OF THE OCEAN .... 17 III. LEGENDARY ISLES 29 IV. THE SARGASSO SEA 39 V. THE NORTHWESTPASSAGE 48 I. THE ATTAINMENT OF THE POLES ... 62 VII. THE EXTENT OF THE OCEANS 77 VIII. THE DEPTHS OF THE SEA 90 K. THE BOTTOM OF THE SEA 104 fK. TPIE LEVEL OF THE SEA 115 V XT. THE SURFACE WATERS 130 XII. THE WATERS OF THE DEPTHS .... 148 XIII. ICE IN THE SEA 166 XIV. WAVES OF THE SEA 176 XV. THE TIDE 203 XVI. TIDAL CURRENTS 228 XVII. OCEAN CURRENTS 245 XVIII. THE GULF STREAM 266 XIX. THE SCIENCE OF THE SEA 289 INDEX 303 ILLUSTRATIONS FIGURE PAGE 1. Westward and eastward routes of Columbus, first journey 26 2. The Sargasso Sea 46 3. Relative areas of land and sea between latitudes 80 N. and 65 S 83 4. Average depth of the sea for each five-degree zone of latitude 97 5. Hypsographic curve of the earths surface .... 102 6. Profile of the South Atlantic Ocean along the twenty second parallel 109 7. Daily sea level, New York Harbor, February, 1919 . 117 8. Monthly sea level, New York Harbor, 1919-1920 . . 118 9. Seasonal variation in sea level, Atlantic coast, . 120 10. Seasonal variation in sea level, Gulf and Pacific coasts 121 11. Seasonal variation in sea level, Honolulu and Manila 122 12. Yearly sea level, New York and San Francisco . . 124 13. Variation of salinity of surface waters with latitude 137 14. Variation of temperature of surface waters with lati tude 143 15. Temperature of surface waters of Atlantic Ocean . 146 16. Observed temperature at various depths at three stations 157 17. Generalized curve of variation of temperature of sea water with depth 159 18. Temperature variation of the sea with latitude . . 163 19. Drift of icebergs in North Atlantic Ocean . . . 173 20. Profile of trochoidal wave 187 21. Rise and fall of the sea in San Francisco Bay, August 26-28, 1883 196ix x ILLUSTRATIONS FIOUBK PAGE 22. Tide record, San Francisco Bay, forenoon of Nov. 21, 1910 198 23. Stationary wave 200 24. Tide curve, New York Harbor, April 22-23, 1920 . . 208 25. Tide curve, San Diego, California, April 22-23, 1920 211 26. Tide curve, Seattle, Washington, April 22-23, 1920 . 212 27. Tide curve, Honolulu, Hawaii, April 22-23, 1920 . . 213 28. Tide curve, Pensacola, Florida, June 1-2, 1926 . . 214 29. Tide curve, Galveston, Texas, June 28-29, 1920 . . 215 30. Combination of a daily with a semidaily tide . . . 216 31...