Extent of the Ocean.--Length of its Coast-Line.--Mural, Rocky, and Flat Coasts.--How deep is the Sea?--Average Depth of the Atlantic Ocean.--The Telegraphic Plateau between Newfoundland and Ireland.--Measurement of Depth by the Rapidity of the Tide-Wave. --Progressive Changes in the Limits of the Ocean.--Alluvial Deposits.--Upheaving.--Subsidence.--Does the Level of the Sea remain unchanged, and is it everywhere the same?--Composition and Temperature of Sea-Water.--Its intrinsic Colour.--The Azure Grotto at Capri.--Modification of Colour owing to Animals and Plants. --Submarine Landscapes viewed through the Clear Waters Page 3 CHAPTER II. THE WAVES OF THE OCEAN. Waves and the Mode of their Formation.--Height and Velocity of Storm-Waves, on the High Seas, according to the Calculations of Scoresby, Arago, Sir James Ross, and Wilkes.--Their Height and Power on Coasts.--Their Destructive Effects along the British Shore.-- Dunwich.--Reculver.--Shakspeare's Cliff. 24 CHAPTER III. THE TIDES. Description of the Phenomenon.--Devastation of Storm-Floods on Flat Coasts.--What did the Ancients know of the Tides?--Their Fundamental Causes revealed by Kepler and Newton.--Development of their Theory by La Place, Euler, and Whewell.--Vortices caused by the Tides.--The Maelstrom.--Charybdis.--The _Barre_ at the mouth of the Seine.--The Euripus 32 CHAPTER IV. MARINE CAVES. Effects of the Sea on Rocky Shores.--Fingal's Cave.--Beautiful Lines of Sir Walter Scott.--The Antro di Nettuno.--The Cave of Hunga.-- Legend of its Discovery.--Marine Fountains.--The Skerries.--The Souffleur in Mauritius.--The Buffadero on the Mexican Coast 45 CHAPTER V. OCEAN CURRENTS. Causes of the Oceanic Currents.--The Equatorial Stream.--The Gulf Stream.--Its Influence on the Climate of the West European Coasts. --The Cold Peruvian Stream.--The Japanese Stream 54 CHAPTER VI. THE AËRIAL AND TERRESTRIAL MIGRATIONS OF THE WATERS. Movements of the Waters through Evaporation.--Origin of Winds.-- Trade-Winds.--Calms.--Monsoons.--Typhoons.--Tornadoes.--Water-Spouts. --The Formation of Atmospherical Precipitations.--Dew.--Its Origin. --Fog.--Clouds.--Rain.--Snow.--Hail.--Sources.--The Quantities of Water which the Rivers pour into the Ocean.--Glaciers and their Progress.--Icebergs.--Erratic Blocks.--Influence of Forests on the Formation and Retention of Atmospherical Precipitations.-- Consequences of their excessive Destruction.--The Power of Man over Climate.--How has it been used as yet? 65 CHAPTER VII. MARINE CONSTRUCTIONS.