Note 165 — VI HUMAN HISTORY

Ibid., p. 23. It is well to lay stress on the fact that all these figures are little more than guesses founded on various observations such as the rate of deposition of sediment by rivers. No conclusions with regard to evolution can be drawn from the supposed length of the whole period or from the supposed length of the subdivisions. Nevertheless the relative length of the different subdivisions as estimated has in all probability some approximation to fact, and thus, whatever may be the real length of the period, the time which elapsed between, say, the beginning of the Pleistocene and the middle of the third genial epoch was at least twice and perhaps three times longer than that which has elapsed since the beginning of the latter epoch to the present day.