GENERAL FEATURES OF THE EARTH. 11 



East Indies, the Pacific, and the Antarctic. London and Paris are 

 situated very near the centre of the land-hemisphere. 



General arrangement of the Oceans and Continents. 1 — Oceans and 

 continents are the grander divisions of the earth's surface. But, while 

 the continents are separate areas, the oceans occupy one continuous 

 basin or channel. The waters surround the Antarctic and stretch 

 north in three prolongations, — the Atlantic, the Pacific, and the In- 

 dian Oceans. The land is gathered about the Arctic, and reaches south 

 in two great continental masses, the occidental and oriental ; but the 

 latter, through Africa and Australia, has two southern prolongations, 

 making in all three, corresponding to the three oceans. Thus the con- 

 tinents and oceans interlock, the former narrowing southward, the 

 latter northward. 



The Atlantic is the narrow ocean, its average breadth being 2,800 

 miles. The Pacific is the broad ocean, being 6,000 miles across, or 

 more than twice the breadth of the Atlantic. The Occident, or 

 America, is the narrow continent, about 2,200 miles in average breadth ; 

 the orient, tho broad continent, 6,000 miles. Each continent has, 

 therefore, as regards size, its representative ocean. This great dif- 

 ference of magnitude has an important bearing on the earth's geologi- 

 cal history. The Pacific ocean, reckoning only to 62° S., has an area 

 of 62,000,000 square miles, or nine and a half millions beyond the 

 area of all the continents and islands. 



(3.) Oceanic depression. — (a.) Outline. — The oceanic depression 

 is a vast sunken area, varying in depth from 1,000 or less to, probably, 

 30,000 feet. 



The true outline of the depression is not necessarily identical with 

 the present line of coast. About the continents, there is often a region 

 of shallow depths, which is only the submerged border of the con- 

 tinent. On the North American coast, off New Jersey, this submerged 

 border extends out for 80 miles, with a depth, at this distance, of only 

 600 feet ; and from this line the ocean-basin dips off at a steep angle. 

 The true outline of the basin on this and other coasts is shown by 



1 In illustration of this part of the work, the reader is referred to the map at the close 

 of the volume. It is a Mercator's chart of the world, which, while it exaggerates the 

 polar regions, has the great advantage of giving correctly all courses, that is, the bear- 

 ings of places and coasts. The trends of lines (" trend " means merely course or bear- 

 ing) admit, therefore, of direct comparison upon such a chart. It is important in ad- 

 dition that the globe should be carefully studied in connection, in order to correct mis- 

 apprehensions as to distances in the higher latitudes, and appreciate the convergences 

 between lines that have the same compass-course. 



The low lands of the continents on this chart, or those below 800 feet in elevation 

 above the sea, are distinguished from the higher lands and plateaus by a lighter shad- 

 ing, and the axes of the mountain-ranges are indicated by black lines. The oceans are 

 crossed by isothermal lines, which are explained beyond. 



