India's civilisation, intimately bound up from its birth with the great social and religious system which we call Hinduism, is as unique as it is ancient. Its growth and its tenacity are largely due to the geographical position of a great and populous sub-continent, on its land side exposed only to incursions from the north through mountainous and desolate regions, everywhere difficult of access and in some parts impenetrable, and shut in on the other two sides of a roughly isosceles triangle by broad expanses of sea which cut it off from all direct intercourse with the West until, towards the close of the Middle Ages, European navigators opened up new ocean highways to the East. India owes her own peculiar civilisation to the gradual fusion of Aryan races of a higher type that began to flow down from Central Asia before the dawn of history upon the more primitive indigenous populations already in possession. Its early history has only now begun to emerge from the twilight of myths and legends, and cannot even now be traced with any assurance of accuracy nearly as far back as that of other parts of the world which preceded or gave birth to our own much more recent civilisation. The pyramids of Ghizeh and Sakkara and the monumental temples of Thebes bore ample witness to the greatness of Egyptian civilisation long before the interpretation of her hieroglyphics enabled us to determine its antiquity, and the discovery of its abundant art treasures revealed the high degree of culture to which it reached. Excavations in the valley of the Tigris and Euphrates have yielded an almost equally valuable harvest in regard to Babylonian and Assyrian civilisation, and Cnossus has told us its scarcely less wonderful story. Yet the long line of Pharaohs was coming to an end and Egypt was losing the national independence which she has never once recovered; Nineveh had fallen and Jerusalem was destroyed; Greece and even Rome had already started on their great creative careers before any approximately correct date can be assigned to the stages through which Indian civilisation had passed. India only becomes historical with the establishment of the Sasunaga dynasty in the Gangetic kingdom of Magadha, which centred in what is now Behar, about the year 600 B.C.