THE earth's contour AND SURFACE SUBDIVISIONS. 23 



main by shallow waters. Vancouver Island and others north of it are 

 similarly a part of North America ; Chiloe, and the islands south to Cape 

 Horn, a part of South America; and so in other cases. In general they 

 correspond to a broader mountain range more or less submerged. 



The oceanic islands are, in general, as has been stated, the summits of 

 submerged oceanic mountain chains. The Atlantic and Indian oceans are 

 mostly free from them. The Pacific contains about 675 islands, with a mean 

 area of only 80,000 square miles. Excluding New Caledonia and some other 

 large islands in its southeastern part, the remaining 600 islands have an area 

 of but 40,000 square miles, or less than that of the state of New York. 



(d) Mean elevation of the land. — The mean height of the continents 

 above the sea has been estimated at nearly 1800 feet, and the mean height 

 of them severally is stated as follows : Europe, 975 feet ; Asia, 2880 ; North 

 America, 2000 ; South America, 1750 ; and Africa, probably about 2000 feet. 

 The material of the Pyrenees spread over Europe would raise the surface 

 only 6 feet ; and the Alps, though of four times larger area, only 22 feet. 



The following estimates have been made for the mean heights of the United States : 

 for the whole area, Alaska excluded, 2500 feet ; Alabama, 500 ; Arizona, 4100 ; Arkansas, 

 650 ; California, 2900 ; Colorado, 6800 ; Connecticut, 500 ; Delaware, 60 ; District of Co- 

 lumbia, 150 ; Florida, 100 ; Georgia, 600 ; Idaho, 5000 ; Illinois, 600 ; Indiana, 700 ; Iowa, 

 1100 ; Kansas, 2000 ; Kentucky, 750 ; Louisiana, 100 ; Maine, 600 ; Maryland, 350 ; Mas- 

 sachusetts, 500 ; Michigan, 900 ; Minnesota, 1200 ; Mississippi, 300 ; Missouri, 800 ; Mon- 

 tana, 3400 ; Nebraska, 2600 ; Nevada, 5500 ; New Hampshire, 1000 ; New Jersey, 250 ; 

 New Mexico, 5700 ; New York, 900 ; North Carolina, 700 ; North Dakota, 1900 ; Ohio, 850 ; 

 Oklahoma, 1300 ; Oregon, 3300 ; Pennsylvania, 1100 ; Rhode Island, 200 ; South Carolina, 

 350 ; South Dakota, 2200 ; Tennessee, 900 ; Texas, 1700 ; Utah, 6100 ; Vermont, 1000 ; 

 Virginia, 950 ; Washington, 1700 ; West Virginia, 1500 ; Wisconsin, 1050 ; Wyoming, 

 6700. (Gannett.) 



The extremes of level in the land, so far as now known, are, 1390 feet 

 below the level of the ocean at the Dead Sea, 1300 feet in the deepest part 

 of the Jordan valley, and 29,002 feet high in Mount Everest of the Himalayas, 

 which have many peaks over 25,000 feet. 



In America, Death Valley, on the southeast border of California, descends 

 480 feet below the sea level. As stated by P. S. Coville, it is 175 miles long 

 and 20 in greatest width, and has the Punpral Mountains, 7000 feet high, on 

 the east, and the Panamints, 11,000 feet, on the west. 



(5) Subdivisions of the surface, and character of its reliefs. — The surfaces 

 of continents are conveniently divided into (1) lowlands ; (2) plateaus, or 

 elevated table-lands ; (3) mountains. The varying levels above the sea 

 make up the reliefs of a continent. The limits between these subdivisions 

 are quite indefinite, and are to be determined from a general survey of a 

 country rather than from any specific definitions. 



Lowlands. — The lowlands include the extended plains or country lying 

 not far above tide level. In general they are less than 1000 feet above the 

 sea; but they are marked off rather by their contrast with higher lands of 



