(=11=) Haug, 1911.1, p. 1807. (=12=) Geikie, J., 1894.1, p. 682; 1914.1, p. 250. (=13=) Dubois, 1894.1. (=14=) Fischer, 1913.1. (=15=) Schwalbe, 1899.1; 1914.1. (=16=) Büchner, 1914.1. (=17=) Volz, 1907.1. (=18=) Elbert, 1908.1. (=19=) Selenka, 1911.1. (=20=) Pilgrim, 1913.1. (=21=) Schwalbe, 1899.1, pp. 227, 228. (=22=) _Op. cit._, p. 223. (=23=) Schwalbe, 1914.1, pp. 601-606. (=24=) Büchner, 1914.1, p. 129. (=25=) Dubois, 1894.1, p. 14. (=26=) Keith, 1912.1. (=27=) Smith, G. E., 1912.1, p. 595. (=28=) _Op. cit._ (=29=) Rutot, 1907.1. (=30=) Boule, 1913.1, pp. 266, 267. (=31=) MacCurdy, 1905.1, pp. 468, 469. (=32=) Geikie, J., 1914.1, p. 251. (=33=) _Op. cit._, p. 255. (=34=) _Op. cit._, p. 238. (=35=) Schoetensack, 1908.1. (=36=) _Op. cit._, pp. 25-43. (=37=) Bonarelli, 1909.1. (=38=) Penck, 1909.1. (=39=) Geikie, J., 1914.1, p. 258. (=40=) _Op. cit._, pp. 257-262. (=41=) Schmidt, 1912.1, p. 181. CHAPTER II ARRIVAL OF THE PRE-CHELLEAN FLINT WORKERS DURING THE THIRD INTERGLACIAL--GEOGRAPHY, CLIMATE, AND THE RIVER DRIFTS--PRE-CHELLEAN FLINT INDUSTRY--THE PILTDOWN RACE--MAMMALIAN LIFE--CHELLEAN AND ACHEULEAN INDUSTRIES--THE USE OF FIRE--THE SECOND PERIOD OF ARID CLIMATE--THE NEANDERTHAL RACE OF KRAPINA, CROATIA The geologic epoch of the arrival of the Pre-Chellean flint workers in western Europe is by far the most important and interesting one before the prehistorian. Upon it depends the question of the duration of the Old Stone Age, the date of appearance of the Piltdown and of the Neanderthal races, and the whole sequence of climatic and geographic changes surrounding the early history of man. After weighing all the evidence very carefully, the balance of opinion seems to sustain the view that this epoch should be placed _after_ the close of the third glaciation and _before_ the advent of the fourth, that is, during the Third Interglacial Stage. Penck estimated that the third warm interglacial stage[S] opened about 100,000 years ago and lasted between 50,000 and 60,000 years. According to the theory that we have adopted in this work, the Third Interglacial and Fourth Glacial embraced the entire period of Lower Palæolithic time, a period of from 70,000 to 100,000 years, much longer than that of Upper Palæolithic time, which is estimated at 16,000 to 25,000 years. GEOLOGIC ANTIQUITY OF THE BEGINNING OF THE STONE AGE