Draining 



and gradually distributed at the right 

 moment. 



Another advantage is to prevent the chilling 

 of the ground caused by excessive evapora- 

 tion. While being reduced to vapour the 

 water chills the objects at the expense of 

 which the evaporation takes place. On 

 having a bath we feel cold because the 

 moisture on our body is evaporated. In the 

 same way water that is constantly evapor- 

 ated from the surface of damp ground chills 

 it and turns it into cold earth ; but if the 

 water is carried away by draining the evapora- 

 tion stops and there is no further chill. A 

 high temperature is always favourable to 

 vegetation. 



Draining is so advantageous that it is not 

 only practised on damp ground, which, with- 

 out it would be altogether unproductive, but 

 also on ordinary arable ground. Whenever 

 the ground contains too much clay, or even if 

 the soil is good but the subsoil is clay, the 

 rain water cannot escape and the earth will 

 be damp and cold. In course of time, how- 

 ever, the ground dries up, but the earth which 

 has not been disintegrated by the action of 

 air, forms into compact lumps, so that the 

 roots are alternately first drowned and then 



191 



