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 loo 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 difticulty 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 



