In endeavouring to trace the sources of foreign influences, we should not always expect to find clues in the mythologies of great civilizations like Babylonia, Assyria, or Egypt alone. The example of the Hebrews, a people who never invented anything, and yet produced the greatest sacred literature of the world, is highly suggestive in this connection. It is possible that an intellectual influence was exercised in early times over great conquering races by humble forgotten peoples whose artifacts give no indication of their mental activity. In Indian Aryan mythology we are suddenly confronted at a comparatively late period, at any rate some time after tribal settlements were effected all over Hindustan from the Bay of Bengal to the Arabian Sea, with fully developed conceptions regarding the World's Ages and Transmigration of Souls, which, it is quite evident, did not originate after the Aryan conquest of Hindustan. Both doctrines can be traced in Greek and Celtic (Irish) mythologies, but they are absent from Teutonic mythology. From what centre and what race they originally emanated we are unable to discover. The problem presented is a familiar one. At the beginnings of all ancient religious systems and great civilizations we catch glimpses of unknown and vanishing peoples who had sowed the seeds for the harvests which their conquerors reaped in season. The World's Ages are the “Yugas” of Brahmanism. “Of this elaborate system ... no traces are found in the hymns of the _Rigveda_. Their authors were, indeed, familiar with the word ‘yuga’, which frequently occurs in the sense of age, generation, or tribe.... The first passage of the _Rigveda_ in which there is any indication of a considerable mundane period being noted is where ‘a first’ or an earlier age (yuga) of the gods is mentioned when ‘the existent sprang from the non-existent’.... In one verse of the _Atharva-veda_, however, the word ‘yuga’ is so employed as to lead to the supposition that a period of very long duration is intended. It is there said: ‘We allot to thee a hundred, ten thousand years, two, three, four ages (yugas)’.”[150] [150] Muir's _Original Sanskrit Texts_, vol. i, p. 46. Professor Muir traced references in the _Brahmanas_ to the belief in “Yugas” as “Ages”, but showed that these were isolated ideas with which, however, the authors of these books were becoming familiar. When the system of Yugas was developed by the Indian priestly mathematicians, the result was as follows:— One year of mortals is equal to one day of the gods. 12,000 divine years are equal to a period of four Yugas, which is thus made up, viz.: Krita Yuga, with its mornings and evenings, 4,800 divine years. Treta Yuga, " " " " 3,600 " Dwãpara Yuga, " " " " 2,400 " Kali Yuga, " " " " 1,200 " Making 12,000 "