Its upheaval above the great sea which submerged all the north-west of the Indian peninsula long after the Himalaya had massed itself as a formidable mountain chain, belongs to a comparatively recent geologic period, and the same thrust upwards of vast masses of cretaceous limestone has disturbed the overlying recent beds of shale and clays with very similar results to those which have left so marked an impress on the Baluch frontier.
They are six in number: (1) Palaearctic, including Europe, Asia north of the Himalaya, and Africa north of the Sahara; (2) Ethiopian, consisting of Africa south of the Atlas range, and Madagascar; (3) Oriental, including India, Indo-China and the Malay Archipelago north of Wallace's line, which runs between Bali and Lombok; (4) Australian, including Australia, New Zealand, New Guinea and Pol y nesia; (5) Nearctic or North America, north of Mexico; and (6) Neotropical or South America.
From such causes the physical conditions of a large part of Asia, and the history of its population, have been very greatly influenced by the occurrence of the mass of mountain above de Iiima- scribed, which includes the Himalaya and the whole tayan elevated area having true physical connexion with that boundary.
The broad mountainous slope by which it is connected with the lower levels of Hindostan contains the ranges known as the Himalaya; the name Kuen-lun is generally applied to the northern slope that descends to the central plains of the Gobi, though these mountains are not locally known under those names, Kuen-lun being apparently a Chinese designation.
The great rivers of northern India - the Ganges, the Brahmaputra and the Indus - all derive their waters from the Tibetan mountain mass; and it is a remarkable circumstance that the northern water-parting of India should lie to the north of the Himalaya in the regions of central Tibet.