126 RELATION TO PHYSICAL CONDITIONS 



small. The bases will be more or less readily removed, as 

 they will be brought in contact with the carbonic acid and 

 other acids (organic?) of the soil to form comparatively 

 readily soluble salts. 



"This process probably plays an important part in the 

 formation of bog-iron ore, which may be regarded as 

 strictly analogous to a hardpan. The deposition of 

 bauxite, for example, or the formation of a silicious con- 

 glomerate is essentially of the same nature. But it should 

 be remembered that in these latter cases when the action 

 has been deep-seated with hot water as the solvent, the 

 reagent has been much more ionized and so is much more 

 efficient as a solvent. 



"An interesting case from southern California has re- 

 cently come to our attention. The soil was shown to have 

 been somewhat compacted under the plow sole. When 

 the irrigating water was applied, this packed region of the 

 soil caused a more or less temporary accumulation of the 

 waters. This soil, as can be readily seen under the micro- 

 scope, contains a large proportion of unaltered mineral 

 fragments, rich in iron and alumina and therefore well 

 adapted to yielding these materials under -the influence 

 of the solvent action of the water; and, as a matter of 

 fact, this packed material is found to rapidly become 

 cemented with iron and alumina, as an examination in 

 this laboratory showed. It is to be regretted that at the 

 ' time this examination was in progress it was not deemed 

 expedient to determine what constituents the irrigating 

 water held which might augment its solvent power. 



"That other agencies are at work in the production of 

 these phenomena may well be the case. For instance, 

 oxidations undoubtedly have a significant role in this 

 connection in breaking up the original minerals. But it 



