26 AGRICULTURAL TEXT-BOOK. 



(d,) Loamy clay =30 to 60 per cent, sand and puro clay. 

 (e,) Sandy loam = 60 to 90 per cent, sand and puro clay. 

 (/J Sandy soil contains no more than 10 per cent, of pure clay. 

 (g,) Marley soils, in which the proportion of lime is more than 

 5, but does not exceed 20 per cent, of the whole weight of the 

 dry soil, (h,) Calcareous soils, in which the lime exceeding 20 

 per cent, becomes the distinguishing constituent, (i,) Vegeta 

 ble soils of various kinds, from garden mould which contains 

 from 5 to 1 per cent., to the peaty soil in which the organic 

 matter may amount to 60 or 70 per cent. These soils are also 

 clayey, loamy, or sandy, according to the predominant character 

 of the earthy admixtures. 



85. The only use of the great bulk of the soil appears to be 

 (a,) the upholding of the plant, and giving it a fing basis from 

 which to spring; (b,) the absorption of gasses, and the imbib 

 ing and retaining of other elements; (c t ) the supplying of 

 water. 



86. The remaining constituents of the soil may be divided 

 into (a,) Organic matter; (b,) and chemical substances and 

 salts, or Inorganic matter. 



87. All soils contain organic matter in a greater or less pro 

 portion. This organic matter consists, in part, of decayed ani 

 mal, but chiefly of decayed vegetable substances ; sometimes in 

 brown or black fibrous portions ; sometimes forming only a fine 

 brown powder intimately intermixed with the mineral matters 

 of the soil ; sometimes scarcely perceptible in either of these 

 forms ; and existing only in a state of organic compounds more 

 or less devoid of color; and at times entirely soluble in water. 

 In soils which appear to consist only of pure sand or clay, or 

 ganic matter in this latter form may often be detected in con 

 siderable quantities. 



88. Chemically the organic compounds of the soil are thus termed : 

 (a,) Crenic acid ; (6,) Apocrenic acid ; (c,) Geic acid; (rf,) Humic 

 acid ; (e,) huniin, (or humus) ; (/,) Ulmic acid ; (#,) Ulmin. Hurnin 



