CHAPTER I. - 
THE MAGNITUDE OF THE SEA. 
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 Tele- 
graphic Plateau between Newfoundland and Ireland.—Measurement of Depth 
by the Rapidity of the Tide-Wave.—Progressive Changes in the Limits of the 
Ocean.—Alluyial 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. 
Or all the gods that divide the empire of the earth, Neptune 
rules over the widest realms. If agiant-hand were to uproot the 
Andes and cast them into the sea, they would be engulphed in 
the abyss, and scarcely raise the general level of the waters. 
The South American Pampas, bounded on the north by 
tropical palm-trees, and on the south hy wintry firs, are no 
doubt of magnificent dimensions, yet these vast deserts seem 
insignificant when compared with the boundless plains of earth- 
encircling ocean. Nay! a whole continent, even America or 
Asia, appears small against the immensity of the sea, which 
covers with its rolling waves nearly three-fourths of the entire 
surface of the globe. 
A single glance over the map shows us at once how very un- 
equally water and land are distributed. In one part we see 
continents and islands closely grouped together, while in another 
the sea widely spreads in one unbroken. plain; here vast penin- 
sulas stretch far away into the domains of ocean, while there 
immense gulfs plunge deeply into the bosom of the land. At 
first sight it might appear as if blind chance had presided over 
this distribution, but a nearer view convinces us that providen- 
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