THE SEA. 3 
other from east to west; the currents of the Pacific are broad and 
slow, those of the other narrow and rapid ; the waves of this are low, 
those of the other very high. If we represent the volume of water 
which falls into the Pacific by one, that received by the Atlantic will 
be represented by the figure five. The Pacific is the calmest of seas, 
and the Atlantic Ocean is the most stormy. 
The Antarctic Ocean extends from the Antarctic Polar Circle to 
the South Pole. 
It is remarkable that one half of the globe should be entirely 
covered with water, whilst the other contains less of water than dry 
land ; moreover, the distribution of land and water—if, in considering 
the extent of the oceanic basins, we compare the hemispheres 
separated by the Equator and the northern and southern halves of 
the globe—is found to be very unequal. 
Oceans communicate with continents and islands by coasts, which 
are said to be scarped when a rocky coast makes a steep and sudden, 
descent to the sea, as, for example, in Brittany, Norway, and the 
west coast of the British Islands. In this kind of coast certain rocky 
indentations encircle it, sometimes above, sometimes under water, 
forming a labyrinth of islands, as at the Land’s End, Cornwall, where 
the Scilly Islands form a compact group of from 100 to 200 rocky 
islets, rising out of a deep sea. The coast is said to be flat when it 
consists of soft argillaceous soil descending to the shore with a gentle 
slope. Of this description of coast there are two—namely, sandy 
beaches, and hillocks or dunes. 
What is the average depth of the sea? It is difficult to give an 
exact answer to this question, because of the great difficulty met with 
in taking soundings, caused chiefly by the deviations of submarine 
currents. No reliable soundings have yet been made in water over 
five miles in depth. 
Laplace found, on astronomical consideration, that the mean 
depth of the ocean could not be more than 10,000 feet. Alexander 
von Humboldt adopts the same figures. Dr. Young attributes to 
the Atlantic a mean depth of 1,000 yards, and to the Pacific, 4,000. 
Mr. Airy, the Astronomer Royal, has laid down a formula, that waves 
of a given breadth will travel with certain velocities at a given depth, 
from which it is estimated that the average depth of the North 
Pacific, between Japan and California, is 2,149 fathoms, or two miles 
and a half. But these estimates fall far short of the soundings 
reported by navigators, in which, however, as we shall see, there are 
important and only recently-discovered elements of error. Du Petit 
B 2 
