It is true that soils formed in this manner by atmospheric and organic actions take a very long time to grow.  It must be remembered, however, that the process is throughout attended by the removal in solution:  of chemically altered materials.

Considerations such as the foregoing must convince us that while the accumulation of the detrital sediments around the continents is largely the result of activities progressing on the steeper slopes of the land, that is,

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among the mountainous regions, the feeding of the salts to the ocean arises from the slower work of meteorological and organic agencies attacking the molecular constitution of the rocks; processes which best proceed where the drainage is sluggish and the quiescent conditions permit of the development of abundant organic growth and decay.

Statistics of the solvent denudation of the continents support this view.  Within recent years a very large amount of work has been expended on the chemical investigation of river waters of America and of Europe.  F. W. Clarke has, at the expense of much labour, collected and compared these results.  They are expressed as so many tonnes removed in solution per square mile per annum.  For North America the result shows 79 tonnes so removed; for Europe 100 tonnes.  Now there is a notable difference between the mean elevations of these two continents.  North America has a mean elevation of 700 metres over sea level, whereas the mean elevation of Europe is but 300 metres.  We see in these figures that the more mountainous land supplies less dissolved matter to the ocean than the land of lower elevation, as our study has led us to expect.

We have now considered the source of the detrital sediments, as well as of the dissolved matter which has given to the ocean, in the course of geological time, its present gigantic load of salts.  It is true there are further solvent and chemical effects exerted by the sea water

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upon the sediments discharged into it; but we are justified in concluding that, relatively to the similar actions taking place in the soils, the solvent and chemical work of the ocean is small.  The fact is, the deposited detrital sediments around the continents occupy an area small when contrasted with the vast stretches of the land.  The area of deposition is much less than that of denudation; probably hardly as much as one twentieth.  And, again, the conditions of aeration and circulation which largely promote chemical and solvent denudation in the soils are relatively limited and ineffective in the detrital oceanic deposits.

The summation of the amounts of dissolved and detrital materials which denudation has brought into the ocean during the long denudative history of the Earth, as we might anticipate, reveals quantities of almost unrealisable greatness.  The facts are among the most impressive which geological science has brought to light.  Elsewhere in this volume they have been mentioned when discussing the age of the Earth.  In the present connection, however, they are deserving of separate consideration.