CHAPTER IV 



DIFFERENT KINDS OF SOU, 



' |.iOUR substances, mingled in very variable pro- 

 J/ portions, enter into the composition of fertile 

 soil, or arable land, namely: sand or silica, clay, 

 limestone, and humus, or vegetable mold. Each one 

 of these ingredients separately would make but very 

 poor soil, quite unsuited for agriculture ; but united, 

 mixed together, they fulfil the conditions necessary 

 to fertility. Arable land generally contains all four, 

 with the predominance sometimes of one, sometimes 

 of another. The soil takes the name of its most 

 abundant constituent. Thus have arisen the names, 

 silicious soil, argillaceous soil, calcareous soil, and 

 humous soil, to designate the fertile lands dominated 

 respectively by sand, clay, limestone, and humus. 

 Compound terms are also used. For example, when 

 it is said of a certain soil that it is argillo-calcareous, 

 it is meant that clay and limestone are its chief con- 

 stituents. 



"Sand consists of particles, more or less minute, 

 of very hard rock, sometimes opaque, sometimes as 

 transparent as glass, and always easily recognizable 

 by its property of emitting sparks when struck with 

 steel. Flint and white pebbles belong to this kind 

 of rock, which is called silex, silica s or quartz. 



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