358 THE BEGOLITH 



ing this table with reference to the lime, a glance at the col- 

 umns for the two regions shows a surprising and evidently 

 intrinsic and material difference approxinriting to the propor- 

 tion of 1 to 14^. This difference is so great that no accidental 

 errors in the selection of analysis of the soils can to any mate- 

 rial degree weaken the overwhelming proof of the correctness 

 of the inference drawn upon theoretical grounds ; viz., that the 

 soils of the arid regions must be richer in lime than those of 

 the humid countries." These remarks hold good also for the 

 percentages of magnesia and the alkalies. From the fact that 

 in humid regions the more soluble constituents are leached out, 

 we may safely infer a corresponding proportional increase in 

 the insoluble constituents. This is also made manifest by the 

 tables, there being a difference of nearly 15% in favor of the 

 humid regions. The table shows, further, a probably greater 

 proportion of ''zeolitic'' material in the soil of arid regions, the 

 assumption being based upon the percentages of soluble silica. 

 Concerning this difference, the author says: 



'*Nor should this be a matter of surprise when we consider 

 the agencies which are brought to bear upon the soils of the 

 arid regions with so much greater intensity than can be the 

 case where the solutions resulting from the weathering process 

 are continually removed as fast as formed by the continuous 

 leaching effect of atmospheric waters. In the soils of regions 

 where summer rains are insignificant or wanting, these solu- 

 tions not only remain, but are concentrated by evaporation to 

 a point that in the nature of the case can never be reached in 

 humid climates. Prominent among these soluble ingredients 

 are the silicates and carbonates of the two alkalies, potash and 

 soda. The former, when filtered through a soil containing the 

 carbonates of lime and magnesia, will soon be transformed into 

 complex silicates in which potash takes the precedence of soda, 

 and which, existing in a very finely divided (at the outset in a 

 gelatinous) condition, serve as an ever-ready reservoir to catch 

 and store the lingering alkalies as they are set free from the 

 rocks, whether in the form of soluble silicates or carbonates.^ 

 The latter have still another important effect. In the concen- 

 trated form, at least, they themselves are effective in decom- 

 posing silicate minerals refractory to milder agencies, such as 

 calcic carbonate solutions, and thus the more decomposed state 



^ See autlior 's remarks on page 363. 



