614 A TREATISE ON METAMORPHISM. 



In various regions the amounts of salts should be determined in the solutions 

 near the bottom of the belt of weathering and in the solutions issuing from 

 the belt of cementation. Such a comparative analytical study has not been 

 made, and we must therefore have recourse to general reasoning for a 

 probable answer to the question of the relative amounts of the salts entering 

 and issuing from the belt of cementation. 



It might be concluded that the actual fact of widespread consolidation 

 due to tilling the openings of the belt of cementation, so fully emphasized 

 in the opening pages of this chapter, is evidence that the amount of material 

 contained in the water issuing from the belt is not so great as that which 

 joins it through percolation. But there are considerations which render 

 this view very doubtful. As shown by numerous analyses, it is certain 

 that large amounts of materials are contained in the spring and seepage 

 waters which issue from the belt of cementation. From general considera- 

 tions, if the character of the compounds transported be ignored, one would 

 expect that this amount would be greater than that which entered the belt. 

 These considerations are as follows : 



As water passes through the belt of weathering* and enters the belt of 

 cementation it may not have been sufficiently long in the belt of weathering 

 and in close enough contact with the various compounds to become sat- 

 urated. Doubtless in many cases of fine soils containing plentiful soluble 

 compounds, where vegetation is abundant and percolation is slow, saturation 

 for many of the compounds may be approached or even attained. But 

 where there are coarse and thin soils underlain by fissured or porous 

 material, it is highly probable that the descending waters are far from 

 saturated when they leave the belt of weathering and join the belt of 

 cementation. After the waters join the belt of cementation they take a 

 longer or shorter journey before issuing at the surface. It has been 

 explained (pp. 584-586) that the general movement of the ground water is 

 exceedingly slow. In many instances also its journey is long — in some 

 areas hundreds of kilometers. In this connection it may be recalled that 

 it was calculated that the waters which issue at Chicago probably entered 

 the ground in central Wisconsin somewhere from one hundred and fifty to 

 two hundred and fifty years before This factor of time, therefore, is of 

 fundamental consequence in the work of the water of the belt of cementa- 

 tion, and it would be strange if the water which has taken a considerable 



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