It is necessary, once more, to remind the reader that the peninsula of India has an area and population roughly equal to the area and population of Europe without Russia. Everyone who has learnt geography at school is familiar with the great triangle, its base in the soaring Himalayan heights in the north, its apex jutting into the Indian Ocean, and marked by the satellite island of Ceylon. To the north, then, is the great mountain barrier, a tangled mass of snowy peaks, glaciers and snowfields, separating the sunny plains of India proper from the plateaux of Central Asia. Beneath them lie wide river basins, sandy and dry as unirrigated Egypt to the west; moist, warm, and waterlogged to the east. To the south of the valleys of the Indus and the Ganges is the central plateau, home of many aboriginal races. This rises on the west into a castellated rampart of hills facing the Arabian Sea, and on the south slopes away into green undulating uplands. So much, at least, of geographical description must be given as a clue to the distribution of the peoples of India. Along the Himalayas, growing stronger in numbers as we go eastwards, are races mostly of a Mongolian type, mingled with purely Indian elements. In the Panjāb and the United Provinces, sending offshoots southwards along the well-watered west coast, are the peoples in whom the traces of Aryan immigration are most visible. In Bengal we find a duskier race, provisionally termed Mongolo-Dravidian, but with a strong infusion, in the upper classes, of western blood. In the south are a still darker population almost wholly Dravidian. It is in the most ancient part of India, in the high plateau of the Deccan, that there still dwell the peoples who are probably the aborigines of the land and use the most purely Indian languages, the various Dravidian dialects. The geologically recent valleys of the Indus and Ganges are the home of races, mingled with aboriginal peoples, whose language and physical features show that in them is a strong strain of immigrant blood. On the Himalayan slopes, in Assam, and especially in Burma, are Tibeto-Burman peoples, with something of a Japanese aspect. Intermingled with all these, in forests and on rough and hardly accessible hills, are scattered many groups of semi-savage folk, of whom little was known till the gradual spread of British rule carried the administrator, the missionary, and finally the anthropologist, into regions once considered unfit for the presence of civilised men.