| (Period of Heidelberg race.) | | | | | | | | | | | | II. GLACIAL STAGE (= Mindel, Kansan) | 1 | 25,000|400,000| 1,300 | | 1st. _Interglacial Stage_ | | | | | | (= Günz-Mindel, Aftonian) | 3 | 75,000|475,000| | | (Period of _Pithecanthropus_ | | | | | | or Trinil race.) | | | | | | | | | | | | I. GLACIAL STAGE (= Günz, Nebraskan)| 1 | 25,000|500,000| 1,200 | +-----------------------------------------------------------------------+ The Postglacial time divisions are dated by three successive advances of the ice-caps, which broadly correspond with Geikie's fifth and sixth glaciations; they are known in the Alpine region as the _Bühl_, _Gschnitz_, and _Daun_. These three waves of cold and humid climate, each accompanied by glacial advances, finally terminated with the retreat of the snow and ice in the Alpine region, the same conditions prevailing as with the present climate. The minimum time estimates of these Postglacial stages and the corresponding periods of human culture, as calculated by Heim,(50) Nüesch,(55) Penck,(52) and many others, are summarized in the Upper Palæolithic (p. 281). GEOLOGIC AND HUMAN CHRONOLOGY There are four ways in which the lesser divisions and sequence of human chronology may be dated through geologic or earth-forming events. First, through the age of the culture stations or human remains, as indicated by the 'river-drifts' and 'river terraces' in or upon which they occur; second, through the age of the open 'loess' stations which are found both on the 'older terraces' and on the plateaus between the river valleys; third, through the age of the shelters and caverns in which skeletal and cultural remains occur; fourth, through the age of the 'loam' deposits, which have drifted down on the 'terraces' from the surrounding meadows and hills. The men of the Old Stone Age were attracted to these natural camps and dwelling-places both by the abundance of the raw flint materials from which the palæoliths were fashioned and by the presence of game.