TABLE OF CONTENTS 



IX 



82 — Actual weight of a soil, 83 — Pore space in soil, 84 

 — The number of soil particles, 85 — Surface exposed 

 by soil particles, 86 — The effective mean diameter of 

 soil particles, 87. 



CHAPTER VIII 

 The Organic Matter of the Soil ..... 

 The source and distribution of organic matter, 88 — 

 Composition of plants, 89 — Decay of organic matter in 

 soils, 90 — Composition of soil humus, 91 — The work of 

 Oswald Schreiner, 92 — Toxic material in the soil, 93 — 

 End products of humus decay, 94 — Carbonized mate- 

 rials of soil, 95 — The estimation of soil organic matter, 

 96 — The estimation of soil humus, 97 — The organic 

 content of representative soils, 98 — The humus content 

 of soil, 99 — The influence of the original material on 

 the resultant humus, 100 — Effects of organic matter on 

 soil, 101 — Maintenance of soil organic matter, 102. 



126-152 



CHAPTER IX 

 The Colloidal Matter of Soils ..... 

 The colloidal state, 103 — The properties of colloids, 

 104 — Colloidal phases, 105 — Flocculation, 106 — Com- 

 mon soil colloids and their generation, 107 — Prepara- 

 tion of colloids, 108 — Colloids and soil properties, 109 

 — Factors affecting colloids, 110 — Estimation of col- 

 loidal content, 111. 



153-169 



CHAPTER X 



Soil Structure 170-197 



Plasticity, 112 — The cause of plasticity, 113 — The 

 importance of plasticity, 114 — Cohesion, 115 — Methods 

 of determining cohesion, 116 — Factors affecting cohe- 

 sion, 117 — Moisture limits for successful tillage, 118 — 

 Control of cohesion and plasticity, 119 — Soil tilth, 120 

 — Granulation, 121 — Forces facilitating granulation, 

 122 — Wetting and drying, 123 — Freezing and thawing, 



