Longest Mountain Ranges of the World. 121 



Then these two bands extend through British Columbia, gradu- 

 ally Avidening as new ranges arise until they obtain a width of 

 500 miles at the boundary line between British Columbia and 

 the United States, and a width of 1,000 miles on the line of the 

 Union Pacific railroad. These two ranges, the Sierra Nevada 

 and the Rocky mountains, come together in southern Mexico 

 and extend as a single range through Central America and the 

 Isthmus of Panama. On entering South America this range 

 again divides, forming the Cordilleran and the Andes systems, 

 and th-ence they extend southward, with a varying width be- 

 tween them of from 40 to 200 miles. They are connected from 

 east to west by several cross-ranges or spurs. From southern 

 Chile the Andes continues as one chain through Patagonia and 

 Tierra del Fuego to Cape Horn. This is the longest and most 

 persistent chain of mountains in the world. The peaks gradu- 

 ally rise in height from north to south until in Chile, Aconcaqua, 

 22,427 feet in height, is the culminating point ; thence southerly 

 the range gradually lowers to an elevation of a few hundred feet 

 only at the Straits of Magellan and Cape Horn. Several vol- 

 cafioes in this long range rise to a greater elevation than any of 

 the non- volcanic peaks. 



In North America the currents of air from the Pacific ocean, 

 in passing over the Coast, Sierras and other ranges, deposit a 

 large portion of their moisture on the mountains. Between 

 these ranges are warm valleys, and the winds chilled in crossing 

 the mountains evaporate the little moisture in these valle3^s, and 

 they are left dry and arid unless irrigated by mountain streams. 

 Thus we have a succession of arid valleys and green mountain 

 ranges moistened with rain and snow, and rich in forests and 

 vegetation. A number of these valleys are enclosed basins, from 

 which the mountain streams have no outlet to the ocean and in 

 some of which saline lakes -are found. 



Mountains of Asia. 



In Asia we have the largest continent, the highest mountains, 

 the most elevated plateaus and the greatest extent of desert land 

 in the world. 



The Pamir, or '' roof of the world " — " the abode of the Gods," 

 as it was called by the inhabitants — is a vast plateau of 30,000 

 square miles area, Avith a north and south extension of about 

 400 miles, and with a mean elevation of 12,000 feet. It is 



17— Nat. Gkog. Mag., vol. V, 1893. 



