OBIGIN AND FOEMATION OF SOILS. 27 



acter, are easy to work, and well adapted to cereals or 

 fruit. 



Peaty or Vegetable Soils. — A peaty or vegetable 

 soil consists almost entirely of vegetable matter, more 

 or less decayed. Such soils are very productive if well 

 drained, and furnished with a sufficiency of the mineral 

 constituents. 



Soils, however, which are best adapted to the purpose 

 of farming do not belong strictly to either of these 

 classes, but are rather those which contain more even 

 proportions of the ingredients ; hence, a further division 

 of soils is usually made, based upon the relative propor- 

 tions of the principal ingredients, sand and clay. 



Loamy Soils. — A soil consisting of a mixture of 

 sand and clay is called a loam; if it contains from ten 

 to twenty per cent of clay, it is a sandy loam; if from 

 twenty to thirty per cent of clay, it is a loam; if from 

 thirty to fifty per cent of clay, a clay loam. Gravelly 

 or limy loams are those in which gravel or coarse sand 

 and lime »are contained in considerable amounts. Loams 

 are suitable for most purposes, and soils of the different 

 natural classes are improved as they approach the char- 

 acter of loams. 



It would be impossible to describe and classify the 

 almost infinite variety of soils which exist in nature, and 

 which are made up from different proportions of the 

 four ingredients mentioned. 



Perfect Soil. — A perfect soil is one which contains 

 the ingredients in perfect proportions : sand, to enable it 

 to absorb air and moisture in proper amounts, and to 

 render it warm and friable ; clay, to keep it cool, and 



