PHYSICAL PROPEETIES OP SOILS. 13 



seldom do the tillage of sixty acres per annum; but on 

 light soils a pair of horses may overtake the work of 

 eighty acres and upwards, except under very laborious 

 rotations of cropping. 



The terms light and heavy, as commonly applied to 

 soils, do not refer to their actual weight, but to their 

 tenacity, and the degree of resistance they will offer to 

 the plow or other implements. Sandy soils are, m 

 the farmer's sense of the word, the lightest of all soils, 

 because they are easiest to work, while in actual weight 

 they are the heaviest soils known. Clay, also, which we 

 call a heavy soil, because stiff and unyielding to the 

 plow, is comparatively a light soil in actual weight. 

 Peat soils are light in both senses of the word, having 

 little actual weight, and being loose or porous. 



Absorljent amd Retentive Powers of Soils. — If there 

 were no other difference in soils than that of texture, that 

 which contained the greatest amount of finely divided 

 matter would possess an advantage over the soils with 

 coarser parts. One cause of this superiority consists in 

 the greater absorptive and retentive power which finely 

 divided matter possesses, due mainly, in all probability, 

 to the immensely greater quantity of internal superfices 

 in a given bulk or weight of the more finely divided soil. 

 The ammonia floating in the atmosphere is continually 

 being washed into soils, in solution with rain-water. 

 Clay, oxide of iron, and the organic matter contained in 

 the soils, perform the important function of absorption. 

 This property of clay may be one of the circumstances 

 , which render clay soils better for wheat than sandy soils. 

 But, although clay contains a larger porportion of this 

 absorbed substance than sands or loams, it cannot be 

 doubted that these must receive from rains the same 

 amount of fertilizing matter as the clay; only they have 

 less ability for retaining it, or at least for storing it up. 



