THE DRAINAGE OF GRASS LAND 5 



that evaporation produces cold, and the more rapid the 

 evaporation the greater the cold. Travellers in the East will 

 recall the delightful surprise experienced when first they drank 

 cool water from a porous jar while the thermometer registered 

 over 100°. Here is an illustration of the conditions which 

 prevail on a hot day with water-logged soil. Under scorching 

 sunshine, the soil when full of water becomes intensely cold 

 immediately beneath the surface. The top crust may feel 

 warm to the touch, but a plunging thermometer forced into 

 the subsoil wiU reveal a difference of many degrees in tem- 

 perature, which the rainfall on the surface is powerless to 

 increase. When the sun's rays cease to fall on undrained 

 land the cold subsoil quickly brings the surface to its own 

 low temperature. This rapid change gi^'es birth to the 

 mists which in autumn are so familiar in the Fens and in the 

 valley of the Thames. Surely there need be no wonder that 

 under these adverse conditions the grass on badly-drained 

 land is late to begin growing in spring and early to cease in 

 autumn. 



An eminent German authority has demonstrated that 

 there is an intimate connection between a warm dry soil and 

 economy in feeding cattle. Friable land absorbs more heat 

 than land which is saturated with moisture, and retains the 

 heat for a longer period. Upon the one animals he warmer, 

 especially at night, than they do upon the other. A large 

 proportion of the food consumed by animals is utilised for 

 the production of the heat which is constantly dissipated 

 from their bodies. It follows that additional food becomes 

 necessary to replace the animal heat lost by the colder 

 surroundings. 



Land which is properly drained comes under the influence 

 of another operation of nature, to the great advantage of the 

 crops upon it. Water would, after it has passed through the 

 surface to the subsoil, be lost to plant life, were it not for 



