438 



COCOA 



CHAP. 



time of the year. 1 Often for the same purpose a dam 

 is made behind the sluice in the main trench, which 

 dam is removed when the rain comes. 



Sometimes a large trap-door sluice is used, which 

 opens only towards the river : when the river sinks, the 

 water in the main trench thrusts open the door of 

 the trap-door sluice and runs out ; when the river rises 

 again, it closes the door. Though these trap -door 

 sluices do not need constant watching to be opened at 



FIG. 130. A small trench separating two beds (plantation " Susannasdaal "). 



low-tide and closed at high-tide, they cannot be wholly 

 left alone, and special care must be taken that no drift- 

 wood or waterweeds come between the sluice-door and 

 the sluice, which would allow the brackish water at 

 high-tide to run into the main trench. 



It will be clear that the building of the embankment 

 and the sluice, but still more the digging of the drainage 

 system, means an enormous expense. For a plantation 



1 In Bulletin No. 13 of the Department of Agriculture in Surinam the 

 Government analyst, Dr. Sack, gives figures of the amount of salt contained in 

 the river-water of different rivers at high-tide and low-tide in the different 

 months. 



