THE EARTH AS A WHOLE 5 



eludes that something Hke 2,000 feet appears to be the Umit to 

 which ground water descends, while in some regions it ceases at 500 

 feet. From this it is estimated that the amount of water present 

 would produce a layer over the surface of the earth between 50 

 and 100 feet deep. Fuller (/:6i, 62, 12) calculates the exact figure 

 at 96 feet, which would be acceptable were it proven that the data 

 on which his calculations are based are ascertained with equal 

 exactness. 



in. THE LITHOSPHERE. This is the solid framework of 

 the earth. It is a nearly perfect oblate spheroid with a polar di- 

 ameter of 12,713.5 kilometers (7,899.7 miles) and an equatorial 

 diameter of 12,756.5 kilometers (7,926.5 miles), corresponding to a 

 meridional circumference of about 40,008 kilometers (24,860 miles), 

 an equatorial circumference of 40,076 kilometers (24,902 miles), 

 and a surface area of 510 million square kilometers (196,940,700 

 square miles). As already noted, the land surface is something 

 over 29 per cent, of this, or about 148.8 million square kilometers. 

 The greatest elevation of the land above sea-level (Mt. Everest) is 

 8,840 meters, which is nearly 800 meters less than the greatest 

 known depth of the sea (9,636 meters). Of the entire earth's sur- 

 face not over three million square kilometers of area lie more than 

 4,000 meters, nor over half a million square kilometers more than 

 5,000 meters above sea-level. The following table shows the per- 

 centages of land within successive strata of 100 meters (Penck- 

 21, {-.145)'. 



Between o and 200 meters, each interval of 100 meters contains 14.6 % 



of the land, or a total of 29 . 2 % 



Between 200 and 500 meters, each interval of 100 meters contains 



9.0 % of the land, or a total of 27.0 % 



Between 500 and 1,000 meters, each interval of 100 meters contains 



3.8 % of the land, or a total of 19.0 % 



Between 1,000 and 2,000 meters, each interval of 100 meters contains 



1.7 % of the land, or a total of 17.0 % 



Between 2,000 and 3,000 meters, each interval of 100 meters contains 



0.4 % of the land, or a total of 4.0 % 



Between 3,000 and 4,000 meters, each interval of 100 meters contains 



o. I % of the land, or a total of i . o % 



Between 4,000 and 8,840 meters, each interval of 100 meters contains 



0.04 % of the land, or a total of 1.9 % 



99- 1 % 



It is thus seen that more than one-half of the earth's surface (56 

 per cent.) lies below the 500-meter contour, and that more than 

 half this lies below the 200-meter contour. Very different values 



