10 ELEMENTS OP 



sideiable degree, are termed clays ; while all the looser 

 soils are termed Ilffht oi free. 



When soils are naturally fertile, or rendered perma- 

 nently so by art, they are termed loa?/is. 



Subsoils are distinguished from soils by the absence 

 of mould. 



Soils may be distinguished according to their texture 

 and constitution, and they may be divided into two 

 classes.— the stiff or strong, denominated Clays, — the 

 light or free, subdivided into the Sandy, Gravelly, and 

 Peaty ; and all these, again, may be distinguished, 



1st, According to their powers of production, when 

 they are termed Rich or Poor ; and 



2dj According to their habitual relation with respect 

 to moisture, when they are termed Wet or Dry. 



THE PROPERTIES OF SOILS AS DETERMINED BY 

 CHEMICAL ANALYSIS. 



Soils consist chiefly of silica, alumina, hme, magnesia, 

 oxide of iron, potassa, and soda, together with a portion 

 of matter derived from organic substances. 



The soil, then, may be chiefly regarded, 



1st, As the instrument for fixing the roots of plants in 

 the ground ; and, 



2d, As a medium for conveying to them the water 

 holding dissolved the different substances which pass 

 into the plant. 



The order in which the principal substances that en- 

 ter into the composition of soils possess an absorbent 

 power, is the following : 



1. Animal and vegetable substances. 



2. Alumina. 



3. Carbonate of Lime. 



4. Silica. 



The following conclusions may be given as deducible 

 from the investigations of chemists : 



1. Soils, in which a large quantity of silica and alumina 



