128 SYLVICULTURE IX THE TROPICS pt.u 



nursery, and not too far from it. The distance from 

 which it will pay to bring water will depend on the 

 nature and size of the nursery, and on the other means 

 of obtaining a water-supply. Where the supply of 

 running water is not constant it may be necessary to 

 construct a storage tank in the upper part of or above 

 the nursery. A supply of water may also be obtained 

 by damming a watercourse or depression, and thus 

 forming a reservoir which becomes filled during the 

 rainy weather. It must be remembered, how T ever, 

 that in the Tropics such reservoirs breed millions of 

 mosquitoes, which may become a source of danger to the 

 health of the establishment. It is, therefore, preferable 

 to have sheets of standing water at some distance. For 

 the same reason puddles in the channels or in any part 

 of the grounds should not be allowed, and tanks should 

 be covered up with wire gauze of sufficiently fine mesh 

 to prevent the access of mosquitoes to the w r ater. 



If the water has to be lifted, a multitude of means 

 may be employed. In large permanent nurseries the 

 most effective and, in the long run, probably the cheap- 

 est is the setting up of a pump worked by an engine 

 which can be driven by steam or petrol according to 

 the cost of fuel obtainable. The power of the engine 

 and diameter of the suction-pipe of the pump will 

 depend on the area to be irrigated. Information on 

 this point can be readily obtained from manufacturers. 

 For smaller areas, pumps worked by draught animals or 

 by men can be set up, or, where the wind blows steadily 

 during the greater part of the year, the pump may be 

 worked by a windmill. For sending up water from a 

 sheet of water to a high bank forcing pumps are also 

 useful. 



Where these more compact machines are not readily 

 obtainable it may be advantageous to utilise some of 

 the methods employed by the natives of the country or 

 in other countries. One of the simplest is the sJiadoof, 

 which is employed not only in Egypt and India, but 

 also in parts of Southern Europe. It consists of a long 



