ASIA 11 less plain of Gobi, just N. of and considerably less elevated than Thibet, is exposed to such extremes of temperature that only the hardiest shrubs can exist. The western plateau is also excessively cold in winter and excessively hot in summer. In northern India the great dif- ferences in elevation occasion great variations of climate within very moderate distances. Over an immense region one may pass in a single day through all the range of climates ; torrid at the foot of the mountains, temperate on their sides, arctic at the top. In southern India regular rainy and dry seasons, occasioned by the monsoons, greatly modify the climate. The direction of the prevailing winds also affects the temperature. On the southern declivity of the Himalayas, in lat. 30 45', the snow line begins at the elevation of 12,982 ft. ; on the northern declivity the warm winds from the Thibetan plateau raise the snow line to 16,630 ft. Asia is rich in minerals. Gold is widely diffused in the Ural and Altai mountains, Chi- na, Persia, and Japan; silver in Siberia, Co- chin China, and India ; copper and iron in very many localities ; mercury in China, Japan, and India. The island of Bauca vies with Corn- wall in the production of tin. Coal has been found in northern China and Japan ; the area of its production is not ascertained. Petro- leum, in its various forms, is abundant in parts of China and India, in Siam and the val- ley of the Euphrates, and on the shores of the Caspian. Salt is common all over the conti- nent. Precious stones are more widely dif- fused in Asia than in any other part of the globe, every variety being found. The mines of India have produced nearly all the great diamonds discovered. The most valuable pearls are those found on the coasts of Ceylon and of the Persian gulf. The geological fea- tures of Asia are considered under the special heads of the different countries and mountain ranges. The continent presents fewer traces than any other of volcanic action. Volcanoes are confined mainly to the peninsula of Kam- tchatka, many of the mountains of which are only masses of lava. The peninsula of Cutch and the delta of the Indus present here and there traces of volcanic action, and are often agitated by subterranean forces. Mt. Ararat is also a volcanic peak. But the long line of islands forming a prolongation of the Asiatic continent is the great volcanic region ; and the Japanese islands are also volcanic. The bro- ken isthmus which connects the Indo-Chinese peninsula with Australia is a great line of fire. From Papua to Sumatra every large island is pierced with one or more volcanic outlets. Java has the largest number. The flora of Asia, while in general similar to that of the other continents in corresponding latitudes, yet presents some peculiarities. Asia is espe- cially the land of spices, odoriferous gums, and medicinal plants. North of the 60th parallel, the ground is perpetually frozen at a very small depth below the surface. Here and there trees are found as high as 70 ; but for the most part the soil is covered with snow and ice for nine or ten months of the year. When this melts the plains are clothed with mosses and lichens, mixed with dwarf willows, and the swamps and morasses with coarse grass, sedges, and rushes. In the far north the plants live between the air and the earth, their tops scarcely rising above the soil, while their roots creep upon the very surface. The few woody plants trail along the ground, rarely rising an inch or two above it. The alix la- nata, the giant of these miniature forests, never grows more than 5 inches high, while its stem, 10 or 12 feet long, lies hidden among the protecting moss. Somewhat further south, a beautiful flora makes its appearance in the brief hot summer. Potentillas, gentians, saxi- frages, ranunculi, artemisias, and many others spring up, blossom, ripen their seed, and die in a few weeks. The Siberian steppes are bounded on the south by forests of pine, birch, and willow. The upper courses of the great rivers are bordered with poplars, elms, and maples. The Siberian pine, with edible seeds, reaches the height of 126 feet; the pinut cem- Jra grows around Lake Baikal almost np to the line of perpetual snow. The greater part of Thibet is sterile. Frost begins early in Sep- tember and continues till May. In some parts snow falls every month of the year. There are, however, many sheltered spots, heated by radiation from the bare mountain flanks, where grains and fruits of every kind flourish. Wheat, barley, buckwheat, and rice are native ; maize has been introduced, and is successfully culti- vated. There are olives, pears, apples, peach- es, apricots, grapes, mulberries, and currants; the various species of melons are noteworthy for their quality and quantity. The Himalayan mountains form a distinct botanical district. Immediately below the snow line the vegetation is of an arctic character; lower down there are forests of pine, oak, walnut, and maple; the flowers are mainly species of rhododen- dron. At an altitude of about 5,000 feet the transition from a temperate to a tropical flora takes place. The transition zone lies between the 35th and 27th parallels of N". latitude, where the tropical flora becomes mixed with that of the temperate zone. The prevailing plants on the Chinese low grounds are glycine, hydran- gea, camphor, laurel, the wax tree, cleroden- dron, rose of China, thuja, and olea fragrans, the flowers of which are used to flavor the finest teas. The India pride, paper mulberry, and other plants cover many of the hills. Of the tea plant there are two main species. The one, bearing small leaves, furnishes the tea consumed at home and exported to Europe and America; the other, with larger leaves, fur- nishes the brick tea consumed mainly in Thibet and N. E. Siberia; as used it is mixed with butter, forming a soup rather than a beverage. Rice is here the most important cereal. The plains of Ilindostan are so completely sheltered
