of nearly four thousand feet. We found it gravelly and desert-like,
covered with cacti, low sagebrush, and other growths. The dim trail
led us to its edge, where we could look down into the
twelve-hundred-foot V-shaped gash which the river had cut into the
dark, crude-looking Archaean 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 carefully the level strata had been fitted to the
shapeless mass beneath it! It all looked like 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 creation. 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 uniformitarianism, 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 its labyrinthian channel so far below us. It is worth
while to make the descent in order to look upon the river which has