The question proposed in the heading to this paper seems a startling one. That the drainage of such a wide continental area as Northern Asia should have been entirely reversed at such a recent geological period as the Mammoth age, so that its present great drains, the Ob, the Yenissei and the Lena, did not exist at all, but their places were taken by other rivers pouring their waters, not into the Arctic basin, but into some great Mediterranean Sea in Central Asia, seems a paradox. It is nevertheless a conclusion which has been forcing itself upon me for a considerable time, and which I should like to be allowed to argue.