of North America--the Laurentian
highland, the Appalachian highland, the plains, and the western
cordillera--are strikingly different in form and structure. The
Laurentian highland presents a monotonous waste of rough hills,
irregular valleys, picturesque lakes, and crooked rivers. Most of it
is thinly clothed with pine trees and bushes such as the blueberry
and huckleberry. Yet everywhere the ancient rock crops out. No one can
travel there without becoming tiresomely familiar with fine-grained,
shattered schists, coarse granites, and their curiously banded
relatives, the gneisses. This rocky highland stretches from a little
north of the St. Lawrence River to Hudson Bay, around which it laps in
the form of a V, and so is known as the Archaean V or shield.

Everywhere this oldest part of the Western Hemisphere presents
unmistakable signs of great age. The schists by their fine crumpling and
scaly flakes of mineral show that they were formed deep in the bowels
of the earth, for only there could they be subjected to the enormous
pressure needed to transform their minerals into sheets as thin as
paper. The coarse granites and gneisses proclaim still more clearly that
they must have originated far down in the depths of the earth; their
huge crystals of mica, quartz, hornblende, feldspar, and other minerals
could never have been formed except under a blanket of rock which almost
prevented the original magmas from cooling. The thousands or tens of
thousands of feet of rock which once overlay the schists and still more
the granites and gneisses must have been slowly removed by erosion, for
there was no other way to get rid of them. This process must have
taken tens of millions of years, and yet the whole work must have been
practically completed a hundred or perhaps several hundred million years
ago. We know this because the selfsame ancient eroded surface which
is exposed in the Laurentian highland is found dipping down under the
oldest known fossiliferous rocks. Traces of that primitive land surface
are found over a large part of the American continent. Elsewhere they
are usually buried under later strata laid down when the continent
sank in part below sea-level. Only in Laurentia has the land remained
steadily above the reach of the ocean throughout the millions of years.

Today this old, old land might be as rich as many others if climate
had been kind to it. Its soil, to be sure, would in many parts be sandy
because of th