6Q PRACTICAL FARM CHEMISTRY. 



clay or slate), and lime (as carbonate or chalk). Clay^ 

 or pure clay, as seen from the far- 



^^TflofiB.'*'' ^^^'® standpoint, is a compound of 

 about forty per cent of alumina — a 

 metalic earth, the oxide of the metal aluminum — and 

 about sixty per cent of silica or sand. The great 

 tenacity of the compound is due to the alumina. 

 The sandy matter contained in it, being in chemical 

 union with the other, cannot be separated from it 

 by mere mechanical means, as washing or boiling. 



Soils are usually classified as follows : 



1. Pure clay, or pipe clay — not often met with to 

 any great extent. 



2. Strong clay, or tile clay, consisting of pure clay 

 and five to fifteen per cent of silicious sand, which 

 latter is easily separated from the clay by washing. 



3. Clay loam, consisting of pure clay with fifteen 

 to thirty per cent of sand, separable by washing. 



4. Loam or ordinary loam, containing pure clay 

 with thirty to sixty per cent of sand. 



5. Sandy loam, containing sixty to ninety per cent 

 of sand. 



6. Sandy soil, containing upwards of ninety per 

 cent of sand. 



7. Calcareous soils, containing five to twenty, or 

 more, per cent of carbonate of lime. According to 

 the proportion of clay and sand contained in them, 

 we call them calcareous clays, calcareous loams, or 

 calcareous sands. 



8. Vegetable moulds, such as rich old garden 

 soils, containing a very large per cent of decayed 

 animal and vegetable substances, as the result of 

 often-repeated, heavy applications of bulky manures^ 

 or peaty and mucky soils, containing thirty to 

 seventy per cent of organic matter. 



