Abstract

Geological and astronomical-authorities place the age of our world at some- where between two and three thousand million years, and that of the consolida- tion of its crust at about two thousand million years. Since then the agents of disintegration and denudation-water, atmosphere, heat, cold, and frost and for some hundreds of millions of years, the roots of vegetation, together with rabbits, moles and earthworms-have, mainly through the solvent action of rain water. transformed the solid rock into sand and clay and transported these products. together with minerals in solution, into the rivers, sens and oceans. The geo- logical formations resulting therefrom after being raised above sea level, have repeatedly been subjected to the same processes of disintegration and denuda- tion. Observation in a railway cutting or quarry will frequently show slightly disintegrated rock at a depth of only a few feet below the surface. Above this the rock can be seen to be in progressive stages of disintegration until, ot the surface, the solid formation has been transformed into fine sand or clay and is ready for erosion by rain and surface flow into adjoining streams. What is now soil on the land surface was but a short time ago, as measured by the geo- logical clock, solid rock some feet below the surface. The rates of disintegra- tion and denudation are clearly interdependent and vary with climatic conditions.

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