26 



CHAPTER III. 



Study of the Soil (continued] Its Complicated Character Soluble Material 

 Fine Impalpable Material Quartzoze Material Calcareous Material 

 Vegetable Matter Stones Complex Functions of Soils Conditions of 

 Fertility Indications of Fertility. 



IN the last chapter I described the action of certain forces 

 which have slowly caused the crumbling down of rocks, and 

 the difference between a soil and disintegrated or powdered 

 rock. Two factors in the formation of soils account for this 

 difference, the first being that of time, and the second being 

 that of vegetation. It is the lapse of time which produces 

 that extraordinary gradation in the condition of the materials 

 forming soils which may be exemplified (1) by the presence 

 of soluble matter ready to be taken up by the rootlets of 

 plants ; (2) by matter in a pulverulent and impalpable con- 

 dition ; (3) by matter in a somewhat coarser condition ; and 

 (4) by means of mineral fragments which may be described 

 as portions of the parent rock or rocks from which the soil 

 was in the first instance derived. 



This diversity of condition in the material confers upon 

 the soil a special power a power which is neither strictly 

 physical nor yet strictly chemical, but which has been 

 termed physico-chemical, a power of surface attraction which 

 may be compared to that of charcoal, spongy platinum, and 

 other porous materials, which condense gases and absorb 

 substances from solution. It is a power which has been 

 compared to that of textile materials to fix dyes in such 



