REPORT OF THE CHEMIST. 155 



IMPORTAITCE OF A PROPER MECHANICAl. CONDITION. 



It is not very difficult to adapt a plant or crop to the nature of the 

 soil when once we know what mineral ingredients are required by the 

 one and furnished by the other; but it demands very close observation 

 and study and a most diligent application of means to bring the physi- 

 cal or mechanical properties of the soil into the state best fitted for pUint 

 growth. 



The influence of mechanical operations becomes obvious, as the access- 

 ibility of air, moisture, and warmth, which are essential to the devel- 

 opment of the changes that occur in the process of germination, are but 

 shghtly influenced by the chemical composition of the soil, being all 

 dependent on its mechanical condition. And this influence is not con- 

 fined to the first stages of growth and development of vegetation, but 

 is required all through the life of the plant, for they cannot avail them- 

 selves of their full amount of food unless the state of the soil admits of 

 the free passage of air and moisture, and is favorable to the extension 

 of the rootlets in all directions. 



VARIATIONS IN THE TEXTURE OF SOILS INFLUENCE THEIR FER- 

 TILITY. 



Soils may vary from the coarsest pebbles and loose sands to the finest 

 and most tenacious clays. Those soils are best adapted to agriculture 

 which consist of a mixture of sand with a moderate quantity of clay 

 and a little vegetable matter. When the sand or other coarse material 

 predominates, the soil is easy to till, and will grow most of the crops 

 which are suitable to the locality ; but it is deficient in the power of re- 

 taining moisture and the soluble and volatile parts of manure. When 

 the clay is in excess, the soil is more difficult to till, and will *probably 

 grow fewer crops, as it retains more moisture, is not easily warmed, 

 does not admit of free access of air, and consequently does not facili- 

 tate the chemical changes in the soil and manure placed on it which 

 are so important to the proper nourishment of the plants. 



K soils differed iu nothing else than that of texture, the one which 

 contained the greatest amount of finely divided matter would possess 

 an advantage over those with coarser parts. One cause of this supe- 

 riority consists in the greater absorj^tive and retentive powers which 

 .finely divided matter possesses, due probably to the immensely greater 

 quantity of surface exposed iu a given bulk or weight of the more finely 

 divided soil. 



THE ABSORBENT AND RETBNTITE POWERS OF SOILS. 



The observations of Sir H. S. Thompson* on the absorbent and re- 

 tentive powers of soil, or the power possessed by soil to deconijiose and 

 retain for the subsistence of the plants the ammoniacal aud other salts 

 which form the most valuable constituents of manure, and the highly 

 important investigations of i*rofessors Way t andYoelckers on this sub- 

 ject, have had a most important bearing on practical agriculture, espe- 

 cially to the rational treatment and application of farm-yard manure and 

 the economical use of artificial manures. 



The investigations of Professor Way have given a new direction to 

 the chemical study of soils, and the subject has been taken up by Liebig, 



"Jour, of the Royal Agricultural Society, vol. xi, p. 68. ilhid., p. 313. 



