5 SYLVICULTURE. 



even in the smallest feeders be at least 8 or 9 inches broad, so 

 as to allow of their being easily cleaned out with a spade. 

 According to the nature of the soil and the degree of wetness, 

 drains may have to be dug from about 10 yards apart in stiff 

 clay to 20 in light soil. They should, if possible, be dug a 

 year or more in advance of planting, as peat-bogs and mossy 

 lands subside considerably ; and they should be frequently 

 inspected to see that they are not getting choked in any way. 

 On deep moors it is better to drain them first of all to a depth 

 of about 3 ft. to let the moor settle gradually and gain in 

 density, than to sink trenches to their full depth at once. But 

 even then it is necessary to open them for about one-third 

 deeper than finally intended to be, in order to allow for 

 subsidence. To drain at any time after planting is always 

 risky, as even old woods may die through the subsequent 

 diminution of soil-moisture and lowering of the water-level. 



The cost of digging drains varies greatly with their size 

 and the kind of soil ; but small drains usually come to about 

 d. to Jd. a running yard, large side-drains f d. to 1 Jd., and main 

 drains 1 Jd. to 2d. a yard for ditches 36 by 30 by 9 in., and more, 

 according to size. Where there are wet patches on hill-sides, 

 the drains should run more or less horizontally along the foot 

 of the slope down which the water comes, so as to intercept it 

 at about a right angle and lead it off from the more or less 

 level stretch ; and the more nearly horizontal each such 

 catchment drain is, the greater is its effect as regards the land 

 between it and the next drain lower down. On flat bogs or 

 marshy land a rectangular network of drains is best. Where 

 the land is practically flat and it is difficult to carry off the 

 drainage water, or where moorpan or any stiff layer has to be 

 broken through, and also when more or less parallel drains are 

 being cut, the spoil earth should be thrown up in mounds well 

 back from the trench or drain, and these can be used for 

 mound-planting (say at 5 ft. by 3 ft. or 5 ft. by 4 ft, = 2904 



