THE SOIT.. 61 



are either sandstones^ limestones, or clays / or a mix 

 lure of two or more of these ingredients. Hence we 

 find that all mineral soils are either sandy, calcareous 

 (limey), or clayey j or consist of a mixture of these, 

 in which one or another usually predominates. Thus, 

 we speak of a sandy soil, a clay soil, etc. These 

 distinctions (sandy, clayey, loamy, etc.) are impor- 

 tant in considering the mechanical character of the 

 soil, but have little reference to its chemical condi- 

 tions of fertility. 



By mechanical character, we mean those qualities 

 Avhich affect the ease of cultivation — excess or defi- 

 ciency of water, ability to withstand drouglit, e(,c. 

 For instance, a heavy clay soil is difficult to plow, 

 retains water after rains, and bakes (juite hard dur- 

 ing drought ; while a light sandy soil is plowed with 

 ease, often allows water to pass through immediately 

 after rains, and becomes dry and powdery auring 

 drought. Notwithstanding those differences iii their 

 mechanical character, both soils may be ver} fertile, 

 or one more so than the other, without reference to 

 the clay and sand which they contain, and which, to 

 cnir observation, form their leading characteristics. 

 The same facts exist with regard to a loam, a calca- 

 reous (or limey) soil, or a vegetable mould. Their 

 )nechanical texture is not necessarily an index to 

 their fertility, nor to the manures required to enable 

 them to furnish food to plants. It is true, that each 

 kind of soil appears to have some general quality of 

 fertility or barrenness which is well known to prao- 

 tical men, yet <^his is not founded on the fact that 



