226 THE ANTIQUITY OF MAN 
flints representing an " industry " of a later date than 
Mr Moir's series which come from under the Red Crag. 
Thus it will be seen that recent discoveries in East 
An^lia carry the history of man in England to beyond 
the" bounds of the Pleistocene epoch — well into the 
Pliocene period. We shall see that M. Rutot had, 
before these discoveries were made in East Anglia, classi- 
fied the Pliocene " industries " represented in the Pliocene 
deposits of the Continent. 
The antiquity represented by the sub-Crag flints cannot 
be calculated with any degree of accuracy. Geologists 
assign to the Pliocene period a duration of over a million 
of years. Estimates of the Pleistocene period, as we shall 
see in another chapter, vary from one hundred thousand 
years to one million five hundred thousand years. The 
more I become familiar with the evidence relating to this 
period, the more my judgment is drawn towards the 
lower estimates. The scale employed in the preceding 
chapters allows for about three hundred thousand years 
for the Pleistocene period. If that allowance is accepted, 
then an equal period must be added to take us back to 
the time of the pre-Crag man. 
So far only passing allusions have been made to the 
glacial cycles which occurred during the Pleistocene epoch. 
Mention was made of a disturbance — due to sub-Arctic 
conditions which followed the Mousterian period. This, 
the last of the glacial phases of the Pleistocene period, 
was recognised by Professor James Geikie,^ who named 
it the " Mecklenburgian " glacial epoch in 1894. Sub- 
sequently, it has come to be known as the " Wilrmien " 
glacial epoch — the term introduced by Professor Penck 
of Berlin in 1903.'^ We have also seen that under the 
Mousterian brick earths at Crayford there are signs of 
a pre-Mousterian glaciation — probably occurring in the 
1 The Antiquity of Man in Europe^ Edinburgh, 1914. In the 3rd 
edition of 'I'hc Great Ice Af^e (1894) Professor Geikie distinguished 
four periods of glaciation, separated by three interglacial phases. In- 
dependent researches led Professor Penck to a similar conclusion. 
- See his later paper, " Das Alter des Menschengeschlechtes," Zeitsch. 
fiir Ethnologic, 1908, vol. .\1. p. 390. 
