THE IPSWICH MAN 227 
Acheulean age. The disturbed appearance seen under 
the brick earths may represent effects of Professor Penck's 
third glaciation, the " Rissien," the " WUrmien " being 
the fourth. The chalky boulder clay belongs to Professor 
Penck's second and major epoch — the " Mindelien." His 
first glaciation — the " Gunzien " — fell in the Pliocene 
period, and corresponds in time to the deposition of the 
Norwich Crag. 
The glacial phases afford the student of ancient man 
a series of milestones to mark his journey into the past. 
Unfortunately, we are not certain of the exact number 
of glacial phases, and, what is still more unfortunate, we 
are not yet in a position to offer a complete explanation 
of their occurrence and recurrence. The day will certainly 
come when their cause, their duration, and their sequence 
will become common knowledge. At the present time, 
the only explanation which answers the needs of those 
who are tracing man's history in recent deposits is that 
put forward by the late Major-General Drayson in 
1888.^ He postulated a secondary rotation of the 
earth — a rotation completed in a cycle of 31,602 years. 
It is unnecessary here, even if the writer were qualified, 
to undertake the task of analysing General Drayson's 
explanation. His work and conclusions are being 
vigorously advocated by Major R. A. Marriott,' D.S.O. 
The important point for us is this, that if Drayson's 
hypothesis is well founded, the last ice age reached its 
maximum about thirteen thousand years ago, a date which 
fits very well with the evidence brought forward by 
geologists. 
1 The Earth's Past History, Chapman & Hall, 1888. 
2 Major R. A. Marriott, D.S.O., The Chancre in the Climate, Marl- 
borough, London, 19 14. 
