(British Museum, Natural History). The problems which we are about to discuss have engaged my attention, both as a geologist and as a zoologist, for nearly thirty years. When in 1895 I began as a boy to study the Pleistocene deposits of the Thames I came “devoted and sincere” like the student in Faust, with implicit trust in my text-book and in the teachings of my elders. And in 1899 when rash enough to write my first paper on this subject, † I said in reference to the writings of Professor James Geikie: In my opinion his conclusions are incontestable in so far as they relate to the Palœolithic era, and have never been satisfactorily answered by those holding contrary views. In the course of time, as my geological work led me further afield, and as my knowledge of the Pleistocene Mammalia became more exact, it became apparent that even the best text-books are very imperfect mirrors for the face of nature, that the best reasoning is sometimes wasted on faulty premises, and that we must not take anything for granted. In attempting to solve the British Pleistocene riddle one of the first steps must be to find a suitable time-scale. Ordinary strati-graphical method, surest of guides when dealing with older formations or with individual Pleistocene sections, here fails us because we have to deal with a great many scattered and isolated deposits. In these circumstances many have sought the basis of such a scale in palaeontology or in the ...