102 Transactions of the Academy of Science of St. Louis 
the assignment of Sinanthropus to the early Pleistocene is on 
the basis of the animal bones occurring in the same travertine 
deposits composed of calcium carbonate. 
The geologist who is accustomed to think in terms of geologic 
events and processes is satisfied with dating a discovery with 
reference to a glacial or interglacial stage, but when the same 
statement is made to the average individual, he generally asks, 
“How many years ago was that?” As nature has the feminine 
characteristic of jealously guarding her exact age, it is best to 
start the answer to this question at a point of reference on which 
| scientists agree, namely that man witnessed the last glaciation. 
The implements of Lower Paleolithic culture were employed by 
intelligent individuals before the close of the glacial period. The 
best known race of this period is the Neanderthal of which no 
less than seventy representatives including seven nearly complete 
skeletons have been found. It is evident that some of the cave- 
dwellers saw the great ice-sheets come and go, so that if we can 
date the beginning of the recession of the last ice sheet, we 
are also setting a minimum for the age of man. The most accurate 
method of measuring glacial time is the varve method of De 
Geer. It is known that water from melting glaciers during the 
summer deposits in lakes a coarse layer of light colored sediment, 
and during the winter a thin layer of dark colored sediment. ‘The 
annual layer of light and dark material is termed a varve. By 
counting the varves DeGeer and Linden found that 13,500 years 
have elapsed since the ice uncovered Central Scandia. But, dur- 
ing the last invasion the ice had extended southward across 
Germany and Poland. To allow time for the retreat of the ice 
from Poland to Central Scandia, the late Father Stephen Richarz, 
S.V.D., estimated another 5,500 years would be needed, or 19,000 
years would be required for the entire retreat from Poland to 
the present limit of the ice sheet. As man existed when the ice 
advanced to northern Germany, additional time must be allowed 
for the advance of the ice to northern Germany. Assuming the 
conservative figure of 1 foot a day as the rate of movement of 
the glacier, it would require 11,000 years for the glacier to move 
the 750 miles from its place of origin in Scandinavia to northern 
