PROPER DEPTH OF DRAINS. 69 



bulk, and can not be approached very closely by teams 

 on either side ; they thus cause a farther loss of land, 

 beside great inconvenience in working. Their banks 

 and sides are nurseries of weeds, so that unless re- 

 gularly cleared out they are extremely liable to become 

 choked, and thus fail to do their work properly. An- 

 other great evil is, that when water falls upon the land, 

 instead of sinking through to the subsoil, it runs away 

 over the surface; washing off fertilizing substances 

 from the richest part of the soil, and carrying them 

 away. 



For these reasons, covered drains are always to be 

 preferred in situations where it is practicable to make 

 them. There are several points of much importance 

 in the construction of such drains. 



First, as to their depth; where a fall can be ob- 

 tained, this should be from 30 to 36 inches. The 

 plants could then send their roots down, and find to 

 this depth a soil free frcm hurtful substances. The 

 roots of ordinary crops often go down three feet, when 

 there is nothing unwholesome to prevent their descent. 

 The farmer who has a soil available for his crops to 

 such a depth, can not exhaust it so soon as one where 

 they have to depend on a few inches or even a foot of 

 surface. Manures, also, can not easily sink down be- 

 yond the reach of plants. On such a soil, too, deep 

 ploughing could be practised, without fear of disturb- 

 ing the top of the drains. The farmer should not, by 

 making his drains shallow, deprive himself of the 

 power to use the subsoil plough, or other improved 

 implements that may be invented for the purpose of 

 deepening the soil. There are districts in England, 

 where drains have had to be taken up and relaid 

 deeper for this very reason. It would have been an 

 actual saving to have laid them deep enotgh at the 

 first. 



