WHY SHOULD LAND BE DRAINED? 373 



The manner in which draining tiles are moulded from moist 

 clay may be learned from Fig. 9, which represents a strong 

 wooden box filled with clay, which, by the pressure of a 

 lever, is forced out through holes which have the shape of 

 the outside of the tile. A plug stands in the middle of 

 each hole (supported from within, so that the clay can en- 

 tirely surround it as it comes out), which makes the bore of 

 the tile. 



WHY SHOULD LAND BE DRAINED? 



There is one condition of soil that is the most favorable 

 for the growth of nearly all agricultural plants that is a 

 condition of porousness, moisture, warmth, and aeration. 

 The roots of plants need to be in a dark place, to be sur- 

 rounded l>y moisture (this is very different from being 

 soaked in water), and to be sufficiently supplied with air. 



There are other conditions of fertility, such as richness 

 in plant-food, &c., w r hich, although of the utmost impor- 

 tance, are apart from our present subject. What we have 

 now to do with is the mechanical state of the soil, as dis- 

 tinguished from its chemical composition and action that 

 is to say, with its moisture, its temperature, the ease with 

 which roots can penetrate it in search of nutriment, and the 

 opportunity for the admission of atmospheric air to their 

 vicinity. 



The effects of drainage on the chemical constitution of 

 the soil, and on the chemical action of its ingredients as 



