GENERAL FEATURES OF THE EARTH. 27 



The great continental mass accords with the law stated ; — high 

 borders proportioned in the case of each to the extent of the bordering 

 oceans, and a general basin-like form. 



(3.) Africa. — Africa has the Atlantic on the west, the larger Indian 

 Ocean on the east, with Europe and the Mediterranean on the north, 

 and the South Atlantic and Southern Ocean on the south. Its system 

 of structure has been well explained by Professor Guyot. As he has 

 stated, the northern half has the east-and-west position of Asia, and 

 the southern the north-and-south of America ; and its reliefs corre- 

 spond with this structure. The Guinea coast belonging to the north- 

 ern half projects west in front of the South Atlantic, and is faced by 

 the east-and-west Kong Range ; and opposite, on the Mediterranean, 

 there are the Atlas Mountains, the High Plateau of which is about 

 8,000 feet, and one peak in the Atlas of Marocco is 18,000 feet high, — 

 although the ridges are generally much lower (5,000 to 7,000 feet),. 

 The two thus oppose one another, like the Himalayas and Altai. The 

 southern half of the continent has a border mountain-range the most 

 of the way along the west and south. On the latter, which has a 

 length of 700 miles, there are three or four parallel ridges, and some 

 of the peaks are 4,000 to 7,000 feet high. Along the southwestern 

 coast, the ranges are 4,000 to 5,000 feet, and on the Guinea coast the 

 Kong Mountains 2,000 feet. Up the eastern coast, there is also a 

 mountain-border, and higher than the western. By these border-ranges 

 the interior of Africa is mostly shut off from the sea : it is a shut-up 

 continent, as Guyot calls it. The loftiest mountains are in Abyssinia 

 and Zai%uebar, facing the Indian Ocean. Abyssinia is, to a great 

 extent, an elevated plateau, 6,000 to 7,000 feet in height, with ridges 

 reaching to 15,000 feet; and, farther south, in 3° 40', stands the snowy 

 Kilima-Xjaro and Ngai, which are 19,000 feet high. 



The interior of the northern or east-and-west half consists of (1) the 

 Great Sahara region, a plateau of about 1,500 feet elevation, with its 

 undulations and ridges, and some elevations of 6,000 feet ; (2) an east- 

 and-west depression on the north, between Sahara and the border- 

 mountains, below the ocean's level in some parts, and being the region 

 of the oases, all of which are 100 to 200 feet below tide level; (3) a 

 partial east-and-west depression about the parallels 10° to 15° N., 

 separating the Sahara plateau from the southern, and containing Lake 

 Tchad, at an elevation of 800 feet. The interior of the southern half 

 is a plateau 2,500 feet in average height. 



Fig. 21. 



b c a e £ N 



The sections Figs. 21 and 22 give a general idea of these features. 



