CHAPTER III. 



FORMATION OF SOII,S. 



OOILS are formed by the weathering and disintegration of 

 rocks. Soils are either sedentary ', that is, formed out of 

 the underlying rocks, or transported^ that is, formed out of 

 the disintegrated parts of rocks, brought down mainly by 

 fluvial action from a distance. Sedimentary rocks contain- 

 ing fossil remains of plants were soils at some ancient geolo- 

 gical period. The superposition of layer after layer of silt on 

 them resulted in their getting compacted and solidified under 

 pressure. By volcanic action these solidified masses coming 

 again to the surface or being bulged up in the form of moun- 

 tains became once more subject to the action of rain and heat 

 and cold and the atmosphere, and once more they were 

 weathered and converted into soils. In geological language 

 the loose top soil is also a rock, and in some future age what 

 is now soil with herbs and trees growing on it, will become a 

 fossil-bearing hard rock with other rocks superposed on it. 

 Underneath the loose matting of earth both in land and in 

 sea there is the uneven pavement of stone, jutting out into 

 high mountains or sinking deep in valleys and ravines or 

 extending far and wide in plains and table-lands. There are 

 mountains and valleys and plains both in sea and on land. 

 The agriculturist is mainly concerned with the loose matting 

 Ojf soil and subsoil on dry land and scarcely at all with the 

 stone pavement underneath, unless it occurs within easy depth, 

 in which case he can get building-stones, coals, or other 

 minerals, or even valuable manurial substances for improving 

 his soil by digging down a short depth or carrying from a short 

 distance. An admixture of 10 to 15% of small stones of the 

 right kinds with agricultural soils, is not undesirable, as these 



