EVOLUTION MADE PLAIN 7 
and lake thousands and millions of years ago. 
In the movements of the earth’s crust the sedi¬ 
ment of ancient sea and lake bottoms was 
raised above the water and became land, the 
sediment hardening into rock. All sediment is 
formed on a level, but in its up-heaval—gener¬ 
ally slow, sometimes violent—it is often tilted 
at various angles exposing its edges. It is 
from this out-cropping, stratified rock (the sum 
of which is often several miles in depth) that 
forms the outer part of the earth’s crust that 
the geologist reads the story of creation. 
The oldest or lowest water-laid rock is the 
archaean in which there are no fossils. Above 
this, in the stratum formed in a later period 
are found evidences of the beginnings of life. 
After millions of years of growth and develop¬ 
ment the shell fish, at the top of the inverte¬ 
brate group, is produced. Then comes a period 
of uncounted millions of years in which the 
fishes, the lowest of the vertebrates, are being 
developed — millions of years to bridge the 
chasm between the two main divisions of the 
animal kingdom; millions of years to produce 
a backbone! Other long periods of time, filled 
with change and development, come and go— 
the age of the coal plant and of the frogs, suc¬ 
ceeded by the age of reptiles, giant monsters, 
cold-blooded and of small brain, swarming sea 
and land. Long ages pass; the reptilian mon¬ 
sters have become extinct, leaving as their rep¬ 
resentatives only a few dwarfed species—the 
crocodile, the lizard, the snake, the turtle. Of 
mammals the lowest orders arrive first, fol¬ 
lowed by the more highly developed until final¬ 
ly man appears. 
