ROADS, BRIDGES AND DRAINS 61 



cutting an additional drain is one of the very best ways of getting 

 rid of the disease of Fomes. 



It is, therefore, absolutely essential at all costs to ensure 

 that land is well drained. Many estates, more especially in 

 Sumatra and the Straits Settlements, leave very much to be 

 desired in this respect. The water-level in the drains is much 

 too high. If the managers and the visiting agents of such 

 estates realized how much the root-systems of the trees 

 were restricted from this cause, and the constant loss of the 

 fertility of the soil which was going on, they would not be 

 content without securing better drainage. 



The curious paradox is sometimes to be witnessed that the 

 trees planted in a heavy, badly-drained, water-logged clay soil 

 suffer from want of sufficient water supplies. The reason of 

 this may not at first be apparent. It is due to the fact that in 

 a water-logged soil the roots of the trees are necessarily confined 

 to shallow surface-layers which the roots soon drain of all 

 available moisture. At the same time the roots have the utmost 

 difficulty in drawing further supplies from beneath, as water 

 only percolates through clay with extreme slowness. As a 

 consequence of this the trees suffer from want of moisture, 

 there is poor root development and a generally-retarded con- 

 dition of growth. Some object-lessons of this are to be seen on 

 a few estates. 



Of course it is wonderful what ill-usage Heveas will with- 

 stand, and under what bad conditions they can be induced to 

 grow. Still, the enormous percentages of vacancies, repeated 

 supplies, and badly-shaped and badly-grown trees to be found 

 on ill-drained estates speak loudly to those who will listen. 



In excavating drains care should be taken that the direc- 

 tion in which they run is in accordance with the natural fall of 

 the land and the direction in which an outlet for surplus water 

 can be secured. One would think this is sufficiently obvious to 

 need no mention, but there have been cases where considerable 

 sums of money have been spent on digging drains which after- 

 wards were found to run in a wrong direction. Too great a 

 slope in the drains will involve too rapid a rush of water and the 

 sweeping away of soil. A fall of about one foot in twenty is 

 about the limit. 



The number of drains to be excavated and their distances 



