62 THE SOIL. 



the clay or the sand, or the vegetable matter, enter 

 more largely into the constitution of plants than they 

 do when they are not present in so great quantities, 

 but on certain other facts which will be hereafter 

 explained. 



As the following names are used to denote the 

 character of soils, in ordinary agricultural descrip- 

 tion, we will briefly ex]>lain their application : 



A Sandy soil is, of course, one in which sand 

 largely predominates. 



Clay soil, one v^here clay forms a large proportion 

 of the soil. 



Loamy soil, where sand and clay are more equally 

 mixed. 



Marl contains from five to twenty per cent, of 

 carbonate of lime. 



Calcareous soil more than twenty per cent. 



Peaty soils, of course, contain large quantities of 

 organic matter.* 



We wull now take under consideration that part 

 of the soil on which depends its ability to supply 

 food to the plant. This portion rarely constitutes 

 more than five or ten per cent, of the entire soil, 

 often much less — and it has no reference to the sand, 

 clay, and vegetable matters which they contain. 

 From analyses of many fertile soils, and of others 

 which are barren or of poorer quality, it has been 

 ascertained that the presence of certain ingre- 

 dients is necessary to fertility. This may be bet- 



* These distinctiona axe not essential to be learned, but are 

 often convenient. 



