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If this were true, could there have been any continental growth at all? Could a city grow by the process of pulling down the old buildings for material to build the new? If the geology is correct, I fail to see how there would be any more land surface to-day then there was in Archaean times. Each new formation would only have replaced the old from which it came.
Slowly or rapidly, they yielded to this disintegrating process, and as the rocky masses broke up, they were washed by the rills and streams into the bed of the sea, where they soon rested upon the tilted ends of the Algonkian strata and exposed surfaces of the Archaean masses, waiting for them. The Deposition of the Tonto Sandstones.
The periods we have already covered the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian form the Primary or Palaeozoic Era, to which the earlier Archaean rocks were prefixed as a barren and less interesting introduction. The stretch of time on which we now enter, at the close of the Permian, is the Secondary or Mesozoic Era.
It is more natural to suppose that millions of years of volcanic activity on a prodigious scale would characterise this early stage, and the "primitive crust" would be buried in fragments, or dissolved again, under deep seas of lava. Now, this is precisely what we find, The oldest rocks known to the geologist the Archaean rocks are overwhelmingly volcanic, especially in their lower part.
The highest group, the Cephalopods, "keep their heads," in the literal sense, and we shall find them advancing from form to form until, in the octopus of a later age, they discard the ancestral shell, and become the aristocrats of the Mollusc kingdom. The last and most important line that led upward from the chaos of Archaean worms is that of the Arthropods.
At this time a large part of North and South America, and of Europe, and parts of Asia and Australia went under the ocean. It was as if the earth had exhaled her breath and let her abdomen fall. The sea united the Gulf of Mexico with the Arctic Ocean, and covered the Prairie and the Gulf States and came up over New Jersey to the foot of the Archaean Highlands.
"Perhaps you are unaware," continued the scientist, "that in both the eastern and western portions of this range, a section running transversely to its main axis presents a complete succession from the oldest Archaean to the newest quaternary." The Professor fixed Stacy with a stern eye. "Do you follow me, young gentleman?" "Ye yes, sir," stammered Chunky weakly, shrinking back against the rocks.
It has the merit of suggesting a reason why life may not be evolving from non-life in nature to-day, although it may have so evolved in the Archaean period. Other students suggest other combinations of carbon-compounds and water in the early days. Some suggest that electric action was probably far more intense in those ages; others think that quantities of radium may have been left at the surface.
It is one of the most instructive "living fossils" in the museum of nature. To understand its significance we must glance once more at an early chapter in the story of life. We saw that a vast and varied wormlike population must have filled the Archaean ocean, and that all the higher lines of animal development start from one or other point in this broad kingdom.
As we saw, one of the early requirements to be fostered by natural selection in the Archaean struggle for life was a "thick skin," and the thick skin had to be porous to let the animal shoot out its viscid substance in rays and earn its living. Now the lowest types of Radiolaria are of this character. They have no shell or framework at all.
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