13 



sorbed, and the acids pass through, generally in combination with lime, or when lime 

 is deficient in the soil, in combination with magnesia or other mineral bases. 



(6) Soils absorb more ammonia from stronger than from weaker solutions of sul- 

 phate of ammonia, as of other ammonia salts. 



(7) In no instance is the ammonia absorbed by soils from solutions of free ammonia, 

 or from salts of ammonia, so completely or permanently fixed as to prevent water 

 from washing out appreciable quantities of ammonia. 



(8) The proportion of ammonia which is removed in the several washings is small 

 in proportion to that retained by the soil. 



(9) The power of soil to absorb ammonia from solutions of free or combined ammo- 

 nia is thus greater than the power of water to redissolve it. 



It may be concluded from the above that in ordinary seasons no fears 

 need be entertained that occasiooal heavy rain storms will remove 

 much ammonia from ammoniacal top-dressings, such as sulphate of am- 

 monia, soot, guano, and similar manures, but in excessively rainy seasons, 

 or in districts that have a large rainfall considerable quantities may 

 be removed from land top-dressed with ammoniacal manure, even in the 

 case of stiff clay lauds. 



GENERAL CONCLUSIONS IN REGARD TO THESE POWERS. 



The general conclusions that may be drawn from the different inves- 

 tigations show that when surface waters charged with the products of 

 vegetable decay are brought into contact with argillaceous sediment, 

 they part to some extent with their potash, ammonia, silica, phosphoric 

 acid, and organic matter, which remains in combination with the soil : 

 whilst, under ordinary conditions at least, neither nitrates, soda, lime, 

 magnesia, sulphuric acid, nor chlorine are retained. The phosphates 

 are probably retained in combination with alumina or peroxide of iron, 

 and the silica and organic matters enter into more or less insoluble 

 combinations.* 



The drainage waters from clay soils, especially if the soil is in a fine 

 state of division, are found to carry off the nitrates, sulphates, chlorides, 

 and carbonates of soda, lime, and magnesia. 



THE POWER OF RETAINING MOISTURE IN THE SOIL. 



The amount of moisture retained by a soil is generally in direct ratio 

 to its contents of organic matter and its state of division. A proper 

 degree of fineness in the particles of the soil is very important to 

 obtain, especially if it is subjected to drought. During dry weather 

 plants require a soil that is both retentive and absorptive of atmospheric 

 moisture, and that soil which has this faculty will evidently raise a more 

 vigorous crop than one without it. The materials which are most in- 

 fluential in soils may be arranged in the following order, when this con- 

 dition of retaining moisture is considered : Organic matter, marls, clays, 

 loams, and sands. 



The Soil of the Farm. 



