BEAINIITG. ^ 225 



ARTICLE 2. 

 Drains. 



Drains may be open or covbked. Open drains are very difficult 

 to maintain, as they are constantly being silted up or choked up 

 with weeds and fallen leaves and twigs. Moreover the best por- 

 tions of the top soil get washed away into them. But, on the other 

 hand, for forest purposes drains are, as a rule, only required for a 

 few years, that is to say, until the crop to be raised has become 

 established. After that the trees either cease to be sensible to 

 swampiness, or themselves constitute most effective drains by 

 means of the transpiration through their leaves. Hence, as the 

 covering of drains, especially the larger ones, is very expensive, it 

 should generally be avoided ; and in cases of absolute necessity 

 it will often suffice to cover only the smaller drains. 



Figures 67-71 represent some simple and cheap, yet effective, 

 methods of covering drains. 



In fascine drains (Fig, 67) cross-billets of wood a a, set up trestle- 

 fashion at regular intervals, support longitudinally laid fascines b, 

 upon which, in order to prevent fine soil washing down through 

 them and choking up the drain, clods of turf c, grassy surface 

 downwards, are packed. The rest of the drain is filled up with 

 part of the excavated soil. 



In small stone or rubble drains (Fig. 68), from a third to one 

 half the depth of the excavation is filled with clean round stones a, 

 which are covered with a layer of turf sods b as in fascine drains. 

 Instead of the turf, or immediately below it, a thin layer of smaller 

 stones c may be packed. 



Fig. 69 represents the usual form of a box drain. The sole a 

 is paved in order to prevent the stones on the sides from sinking, 

 and should be laid with the greatest care and with the largest 

 stones. In building up the sides, a few small stones b may be 

 packed under and about the larger ones c in order to steady them 

 as well as the covers d, which last should be placed with their flattest 

 or most concave side downwards so as maintain the cavity as large 

 as possible. If required, small stones, with a covering of sods 

 may be packed over the box. 



Fig. 70 shows two styles of couple drains, the triangle formed 

 by the stone slabs being inverted in B. As in box drains, a packing 

 of small stones, topped with turf, may be laid over the drains. 



