TIME AND CHANGE 
Archean rock. How distinctly it looked like a new 
day in creation where the horizontal, yellowish-gray 
beds of the Cambrian were laid down upon the dark, 
amorphous, and twisted older granite! How care- 
fully the level strata had been fitted to the shapeless 
mass beneath it! It all looked Hke the work of a 
master mason; apparently you could put the point 
of your knife where one ended and the other began. 
The older rock suggested chaos and turmoil; the 
other suggested order and plan, as if the builder had 
said, “Now upon this foundation we will build our 
house.” It is an interesting fact, the full geologic 
significance of which I suppose I do not appreciate, 
that the different formations are usually marked off 
from one another in just this sharp way, as if each 
one was, indeed, the work of a separate day of crea- 
tion. Nature appears at long intervals to turn over a 
new leaf and start a new chapter in her great book. 
The transition from one geologic age to another 
appears to be abrupt: new colors, new constituents, 
new qualities appear in the rocks with a suddenness 
hard to reconcile with Lyell’s doctrine of uniform- 
itarianism, just as new species appear in the life of 
the globe with an abruptness hard to reconcile with 
Darwin’s slow process of natural selection. Is sudden 
mutation, after all, the key to all these phenomena? 
We ate our lunch on the old Cambrian table, 
placed there for us so long ago, and gazed down 
upon the turbulent river hiding and reappearing in 
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