V1U CONTENTS 



PAGES 



fluence upon moisture content of soils ; Farm manures 

 and soil moisture ; Relation of soils to heat ; Heat re- 

 quired for evaporation ; Influence of drainage upon soil 

 temperature ; Specific heat of soils ; Cultivation and soil 

 temperature ; Heat from chemical reactions within the 

 soil ; Heat and crop growth ; Organic matter and iron 

 compounds; Color of soils ; Odor and taste of soils ; Power 

 to absorb gases ; Relation of soils to electricity ; Impor- 

 tance of physical properties of the soil. 



CHAPTER II 



GEOLOGICAL FORMATION AND CLASSIFICATION OF SOILS 54-70 



Agricultural geology ; Formation of soils ; Action of 

 heat and cold ; Action of water ; Glacial action ; Chem- 

 ical action of water ; Action of air and gases ; Action of 

 microorganism ; Action of vegetation ; Action of earth- 

 worms ; Action of wind ; Combined action of the various 

 agents ; Distribution of soils ; Sedentary and transported 

 soils ; Rocks and minerals from which soils are derived, 

 ' as quartz, feldspar, mica, hornblende, zeolites, granite, 

 apatite, limestone, kaolin ; Disintegration of rocks and 

 minerals ; Value of geological study of soils. 



CHAPTER III 



THE CHEMICAL COMPOSITION OF SOILS . . . 71-115 



Elements present in soils ; Classification of elements ; 

 Combination of elements ; Forms in which elements are 

 present in soils ; Acid-forming elements, silicon, double 

 silicates, carbon, sulphur, chlorine, phosphorus, nitrogen, 

 oxygen, hydrogen; Base-forming elements, aluminum, 

 potassium, calcium, magnesium, sodium, iron ; Forms of 

 plant food ; Amount of plant food in different forms in 



