The mean height of the land has been estimated at 2,440 feet, and the mean depth of the sea 11,470 feet. The highest mountain (Mt. Everest) is 29,000 feet high, and the greatest depth of the ocean is supposed to be 31,614 feet.
The North American continent has an area of 6,446,000 square miles, with exceeding 115,000,000 inhabitants, or a little less than 18 to the square mile.
The South American continent has an area of 6,837,000 square miles, with over 45,000,000 inhabitants, or about 6-1/2 per square mile.
Europe has an area of about 3,555,000 square miles, with a population of somewhat less than 400,000,000, or about 107 per square mile.
Africa has an area of 11,514,000 square miles, and a population of about 127,000,000, or 11 to the square mile.
Asia has an area of 14,710,000 square miles, with a population estimated at about 850,000,000, or a little less than 58 to the square mile.
Australia, New Zealand, and contingent islands, have an area of 3,288,000 square miles, with a population of exceeding 5,200,000, or about 27 to the square mile.
It is estimated that the surface of the earth is divided into somewhat more than 28,000,000 square miles of fertile soil, about 14,000,000 square miles of steppe, a little more than 4,000,000 square miles of desert, with the polar regions occupying nearly 5,000,000 square miles of land, most of which is covered with ice.
At the time of Emperor Augustus, there were said to be between 54,000,000 and 55,000,000 people upon the earth, but as the earth undoubtedly supported millions of inhabitants unknown to civilization, these figures are of little consequence.