Himalaya (properly Himālaya; from two Sanskrit words meaning 'snow-abode') is, strictly speaking, the southern escarpment of the great Central-Asian plateau so far as it falls between the Indus and the Brahmaputra. Thus limited, it extends from 73° to 95° E. long., over a distance of some 1500 miles. The Himalayas are not a single range, but a system of for the most part parallel ranges lying obliquely to the general direction of the system. They front the plain of the Ganges in northern India like a stupendous mountain wall, bending back in the west like a scimitar, the sharp edge turned next India. On the east the system is connected with the mountain-ranges of south-west China and northern Burma and Siam. On the north it is backed by the lofty plateau of Tibet, which ranges in elevation from 10,000 to 17,000 feet. At its north-western extremity it runs up into the Pamir plateau, from which radiate also the Hindu-Kush and the Kuen-Lun Mountains. The southern foot of the system rests upon the plain of the Ganges, which nowhere rises more than 1000 feet above the level of the sea. The edge of the outermost hills is skirted, for a distance varying in width from 10 to 15 miles, by a belt of swampy grass-land, traversed by numerous sluggish streams. These in many places overflow and form standing swamps, fringed with gigantic reeds. This belt, called the Tarai, does not extend west of the point where the Ganges breaks through from the mountains. These districts, owing to the great quantity of stagnant water and the great profusion of rank vegetation, are extremely unhealthy; many parts reek with fevers of a very malignant type. Next above the Tarai lies a belt of forest of about the same width, called the Bhabar. Its soil consists of sand, liberally strewn with shingle beds and boulders. The waters of the minor streams that come down from the higher mountains are generally absorbed by this spongy talus-slope, and, passing through it underneath the surface, accumulate again on the upper edge of the lower-lying Tarai.
Above the Bhabar rise the foot-hills of the Himalayan system, generally designated the Siwalik Hills, or sub-Himalayan ranges. They vary in height from a few hundred feet up to 4000, and present steep faces to the plains; on the northern side the slope is gentler, being mostly met at short distances from the summit by the southern flanks of the inner ranges. Geologically the Siwalik Hills belong to the Tertiary formation, and to the Pliocene rather than to the Mioecne period. From the ranges near the Jumna great quantities of fossils, mostly mammals and reptiles, all land and fresh-water animals, have been obtained. It is on the north side of the Siwalik foot-hills that the first mountains appear. They rise up abruptly to elevations ranging for the most part from 7000 to 10,000 feet, and cover a surface zone of 50 miles in breadth. This division embraces a large number of irregular ridges, characterised by great complexity of geological structure. They yield marine fossils. On these ranges stand the sanatoriums, such as Simla, Darjiling, Almora, &c., which are so essential to Europeans during the hot months. The space between the outer members of these ranges and the Siwalik foot-hills is occupied by narrow, shallow, longitudinal valleys, called Dun in the west and Mari in Nepal. They are partly covered with loose shingle and boulders, partly worn into terrace-like steps, partly broken by low, obliquely lying, watershed ridges, which throw off numerous small streams.
In the Himalayas proper two main axes can be determined with tolerable distinctness. One, the southern, contains the line of the great snowy peaks; the other, the northern, forms the watershed between the rivers of India and the rivers of Tibet. The mountains in the southern chain are amongst the loftiest in the world; a very great number of them exceed 20,000 feet ( miles) in height. One of these, Mount Everest (29,002 feet), is the highest measured mountain in the world. Other lofty peaks in this division of the Himalayan system are Mount Godwin-Austen (28,265), the second highest in the range; Kinlehinjina (28,156); Dhaulagiri (26,286); Nanda-Devi (25,700); Trisul (23,400), and several others more than 22,000 feet in altitude. The chain of great snowy peaks is, strictly speaking, a series of mountain-groups, each of which is connected with the watershed chain to the north by a transverse ridge, covered with snow and frequently bearing on its shoulders peaks that tower up to the height of 25,000 feet. Graham, who in 1883 ascended Kabru to a height of 23,700 feet, believed that there are other peaks which will be found to exceed Mount Everest in altitude, for the central parts of the system next Tibet have not yet been surveyed or even explored with anything approaching to thoroughness, mainly because of the jealousy and exclusiveness of the Tibetan authorities, within whose territory much of the loftiest region of the Himalayas falls. These transverse spurs from the northern chain, terminating in stupendous mountain knots, form deep valleys on either side in the space between the two chains. These deep valleys, fringed with overhanging glaciers, are the cradles of the great rivers of northern India. Here are the sources of the Ganges and the Indus and the Brahmaputra, and of hundreds of rivers and streams whose waters eventually reach the ocean through the mouths of these three great channels. The rivers of the Himalayas mostly make their way through the mountains at the bottom of wild and narrow gorges, often several thousands of feet deep, the path through the various chains being mostly at right angles to the strike of the ridge. The inclination of the rivers is, however, nowhere very steep, except along one line: about ten miles south of the chain of great peaks the rivers descend about 5000 feet in the course of a few miles.
This indicates that the whole region must at one time have been bodily upheaved, and before the period of upheaval there existed here a natural ridge or fold of the earth. Geologists indeed believe that the entire site of the Himalayan system, taken in its widest extent, in which it embraces the whole of the Tibetan plateau as far as the outer Kuen-Lun Mountains, was in distant geologic ages the bed of a vast sea or ocean. The mountains are believed to be the result of the action of mechanical forces, such as horizontal compression and tension, combined with lateral stress and strain, operating upon the cooling crust of the earth in a region where, owing to the recent evaporation of the ocean, it was softest and most pliable, and therefore offered least resistance. The rocks of this part of the system are principally crystalline gneiss and mica schist, with veins and zones of granite intruding. The snowy region of the Himalayas is plentifully studded with glaciers, some of them of great extent: one has been surveyed in the western part of the system 36 miles in length. In the same region they descend to 11,000 and 12,000 feet, in the eastern part of the system not lower than 13,000 and 14,000 feet; and on the Tibetan side they are seldom found to come lower than 15,000 and 16,000 feet. This difference is partly due to the difference between the angles of declivity on the north and on the south sides of the chief ranges, partly also to differences in climatic conditions, the principal being the heavier snowfall and the greater rainfall which take place on the south, and the greater dryness of the atmosphere on the Tibetan plateau. Conformably with these facts, the snow-line ranges higher on the Tibetan side than on the Indian: whereas, on the watershed chain, it seldom descends lower than 18,000 feet, and on the tableland remains at 20,000, on the southern faces of the mountains it runs at 15,000 or 16,000 feet. The watershed chain has been little explored; it lies chiefly within Tibetan territory. The only exception to the former statement occurs on the west, where the Mustagh range, which is crossed by the pass of Karakoram (18,350), towers above the mountain valley of Kashmir, forming its northern wall, as the Pir-panjal, a range of the outer Himalaya division rising to 14,000 or 15,000 feet, shuts it in on the south. This watershed chain forms an almost continuous line of peaks, its crest being probably over 18,000 feet in elevation. So far as is known, it is only broken by one pass of less altitude than 16,000 feet, namely the Dras pass leading from Kashmir, which is 11,300 feet above sea-level. The Niti Pass (16,676), south-east of Ladak, connects the best roads from India and from East Turkestan.
The Himalayas possess few lakes. In the east, north of Sikkim, are Yamdok-cho or Palti, 45 miles in circumference, with an island, 2000 to 3000 feet high, in the centre; and Chomto-dong, 20 miles long by 16 broad, at an altitude of 14,700 feet. More to the west lie the holy Tibetan lakes of Manasarovar and Rakas Tal, which give birth to the river Sutlej. Besides these there are Nainital in Kumaon and the Lake of Kashmir. In nearly all parts of the Himalayas metallic ores have been ascertained to exist. But gold, iron, copper, and lead are the only minerals extracted. Gold is largely mined in Tibet; copper and iron ore are worked in Kumaon and Garhwal.
In the lower, hotter, and moister parts of the Himalayas, chiefly towards the east, the flora is closely related to that of the Malay Peninsula and islands. Farther west, as the drier, colder parts are approached, it approximates to the European flora. On the lower ranges the chief vegetative forms are sals, sissus, bamboos, palms, acacias, rhododendrons, ferns, orchids, &c. in the east, and oaks, pines, spruces, firs, cedars, deodars, and others in the west. On the highest ranges the principal trees are conifers and poplars, with a great variety of alpine plants. The European beech does not grow on the Himalayas. Cultivation does not ascend higher than 7000 feet, except in a few of the warmer valleys. The plants of greatest commercial importance cultivated on the Himalayan slopes are tea and cinchona. In respect of its fauna this region is one of the richest in the world, particularly in birds. Among the more remarkable animals may be mentioned bears, wild cats, leopards, tigers, sun-bears, cat-bears, yaks, musk-deer, wild goats, wild sheep, wild dogs, flying squirrels, the bamboo-rat, and water-shrews. Insects are almost as numerous as birds.
Within Indian territory most of the inhabitants of these mountains are Hindus. The Tibetan portions are occupied by peoples of Turanian stock. No statement can be given of the total number of these mountaineers; many of them live in remote valleys, and are almost unknown, whilst many others dwell outside the limits of the British dominions. In Hindu mythology these majestic mountains are invested with great sanctity. Thousands of pilgrims travel year after year to the holy sources of the Ganges. The temples they visit stand beside the glaciers from which the river emerges, at Gangotri, Kedarnath, and Badrinath. Other temples, scarcely less sacred, stand beside the source of the Jumna at Jamnotri.
See Medicott and Blanford, Manual of the Geology of India (3 vols. Calcutta, 1879); J. D. Hooker, Himalayan Journals (2 vols. Lond. 1854); the works of B. H. Hodgson; Godwin-Austen, in Journ. As. Soc. Bengal (1867-75); and Proc. Roy. Geog. Soc. (1883 and 1884); W. W. Graham, in Proc. Roy. Geog. Soc. (1884); Clements Markham, Boyle in Tibet and Manning in Lhasa (1876); T. Saunders, in Geog. Mag. (1877); Sir H. Strachey, in Roy. Geog. Soc. Journ. (vol. xxiii.); Memoirs of Geological Survey of India; A. Wilson, Abode of Snow (1875); Strachey, The Himalaya (1890); and Sir W. M. Conway, Climbing in the Karakoram Himalayas (1894).