PHYSICAL PROPERTIES OF SOILS. 11 



Another mode in which peat is formed is by the gradual 

 accumulation and decomposition of aquatic plants in 

 shallow lakes and stagnant pools. This kind of peat is of 

 a more loose and spongy quality. What has greatly con- 

 tributed to its formation is the destruction of ancient 

 forests, either by the operation of some natural cause, or 

 by the hand of man. When water gets collected or choked 

 up, as in a morass for instance, many plants contrive to 

 grow in it, and by their decay form peat — especially the 

 " bog moss," which, while it grows above, decays beneath. 



CHAPTER XL 

 PHYSICAL PROPERTIES OF SOILS. 



Texture — Absorbent Power — Temperature. 



Soils differ greatly, not only in chemical constitution, 

 but also in physical characteristics; and, in our estimate 

 of them, we must be guided by their climatic and physical 

 relations no less tban by the results of chemical analysis. 

 It is comparatively easy to adapt the plant or crop to the 

 nature of the soil when once we know what mineral in- 

 gredients are required by the one and afforded by the 

 other; but it demands close observation and a more dil- 

 igent application of means to bring the physical or 

 mechanical qualities of the soil into the state most con- 

 ducive to the growth of its natural products. The nec- 

 essary influence of mechanical ojierations here becomes 

 obvious, for the circumstances of air, moisture, and 

 w^armth, which are essential to the development of the 

 changes wliich occur in the process of germination, are 

 but slightly influenced by the chemical properties of the 



