MAN FROM THE FARTHEST PAST 
about and bending under the loads of detritus which the 
rivers bring down to the plains and the sea, as the winds 
and waters plane the mountains down. Again and again, 
as geology teaches us, portions of the continents have been 
uplifted, planed down, sunk beneath the oceans, covered 
with mud layers, newly uplifted into mountains, newly 
planed down, and so on through vicissitude after vicissi- 
tude in the great age of the earth. Similar changes are still 
going on, slowly, but probably no more slowly than they 
always have done. During many of these changes life 
existed, the remains of which were sometimes buried by 
sands and mud that became rock and so have preserved 
for us the fossil records of the past. 
It is impossible to determine accurately in years the 
length of the periods of geologic time. Moreover, the 
records are fragmentary, imperfect, depending on the 
vicissitudes of elevation and depression, aridity, tempera- 
ture, and other factors. Nowhere is the whole gamut of 
strata from earliest to latest time exposed. The laying 
down of strata demands locations such as the shores of a 
sea or lake, the sea bottom, river basins, or desert valleys. 
Obviously, these could not in all ages prevail at any one 
lace. Yet the earth’s surface yields so many examples of 
the burial of multitudes of forms of life at successive depths 
that what is lost in one locality may be supplied from an- 
other. Thus it has become possible for paleontologists to 
estimate the approximate order of succession of life re- 
corded in the fossil remains, and the approximate relative 
length of time involved in the several periods which these 
fossil remains suggest. These data are confirmed by many 
samples from many parts of the earth’s surface. Local 
contradictory evidences, explainable on grounds of earth- 
folding, noncontemporaneousness of life forms, and other- 
wise, become no more than the exceptions which prove 
the rule. The broad features remain surely known. 
In this brief survey of present hypotheses and observa- 
tions relating to the place of man and his abode in time 
[10] 
