Asia contains many great mountain chains, the chief of which are the Himalaya Mountains, which run along the centre of its southern part and contain some of the highest peaks in the world; the Dhawalagiri is 28,072 feet high, but there are some others supposed to be as high. The Altai or Gold Mountains, forming a boundary to the lowlands of Siberia, the highest peak of which is called the Katunia Pillars, and is 11,000 feet high. The Thain-schan or Celestial Mountains, the Kuen Lun, and the Hindoo Coosh, all of which run pretty nearly east and west, while the ranges called Uralian, Bolor, Khingan, and Chinese chains run nearly north and south. Africa is somewhat triangular, with its base towards Asia and its apex pointing southward. It is bounded northwards by the Mediterranean Sea, and at its east side by the Red Sea and Indian Ocean, while the Atlantic flows on its south-west side. In Africa is the largest desert in the world, the Great Desert of Sahara; it occupies nearly all the northern part, the southern has but few mountains of great extent, but from their elevation and the amount of waters brought down by rivers, it is supposed that the centre has very high table lands. At the north-western part is an extensive mountain system (the Atlas) covering with its branches nearly 500,000 square miles, and sending its slopes to bound the great Desert northwards. The great tract of land comprising North and South America extends in a longitudinal direction pretty nearly north and south through 130 degrees of latitude, or nearly 8000 miles. This great tract is divided by a narrow neck of land (the Isthmus of Panama) into two pretty equal portions; the northern part is peculiar, from containing a number of lakes of immense extent, deserving well the name of inland seas, and both northern and southern divisions for the great number and extent of their water-courses. The whole of this great tract of land is traversed from end to end by an extensive chain of mountains, the longest in the world; at its southern part it forms the Andes, from which a range is continued through the Isthmus, and onwards to form the Rocky Mountains. In the southern division this immense chain passes on the west side of the land close to the sea, is of great elevation in some parts, has some of the highest mountain peaks in the world, and volcanoes also, the highest being in the Andes (Popocatapetl is about 16,000 feet high); but from the western side of the continent the land descends gradually to the eastern. In South America are some of the highest table-lands known, great elevated tracts in connection with the mountain ranges. Australia in its interior is but little known, but the whole aspect of the island appears to be flat, and to have but little elevation, while Greenland and the great tracts of the northern regions beyond, deserve more the name of glaciers, being almost entirely a mass of barren rocks and snow.