294 The Realm of Nature CHAP. 



379. Asia, the highest as well as the largest of the 

 continents, has an average elevation of more than 3000 

 feet. The zone of heights between 600 and 1500 feet is 

 narrower than in any other continent, and more than one- 

 sixth of the surface stands more than 6000 feet above the 

 sea. The orographical centre of Eurasia is formed by the 

 lofty plateau of Pamir (in 38 N. and 73 E.), as large as 

 Ireland, and rising to 25,800 feet above the sea in its 

 highest summit, while its lowest point is 9000 feet ; it is 

 called by the dwellers in the region "The Roof of the 

 World." From this centre, mountain chains spread out 

 like the ribs of a fan to the east and to the west. The 

 lofty range of the Hindu Kush cleft by a few snow-blocked 

 passes and rising into summits 24,000 feet high runs south- 

 west from the Pamir, separating the low plain of India 

 from the low plain of Northern Asia. It branches in lower 

 ridges to the south and west, enclosing the internal drainage 

 area of Iran (Persia), which lies at an average height of 

 3000 feet. The northern mountain ridge, sweeping round 

 the south shore of the Caspian as the Elburz Range, merges 

 into the broken Plateau of Asia Minor. Here the southern 

 ranges also converge, walling the Plateau of Iran from the 

 low plain down which the Tigris and Euphrates pour into 

 the Persian Gulf. Mount Ararat, 17,000 feet above the 

 sea, is the grandest summit in Asia Minor. The plateau 

 spreading southward occupies Arabia, most of which is an 

 internal drainage area. One of the most perfect types of a 

 mountain chain of elevation is presented by the Caucasus, 

 which runs from the Black Sea to the Caspian as a magnifi- 

 cent barrier between the high plateau of Asia Minor and the 

 low, level plain of Europe, and culminates in Mount Elbruz, 

 18,500 feet high. In the calculation of elevation in the 

 tables of 355 this chain is assigned to Europe. 



380. Eastern Asiatic Mountain System. The moun- 

 tain chains which radiate eastward from the Pamir con- 

 verge at two centres, one near the north of the Indo-China 

 peninsula, the other near the Sea of Okhotsk. Between 

 these three knotting points the long mountain ranges seem 

 on the map to droop in graceful folds. They define an 



