PBOrCt DEPTH OF MtAINS. 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 olF 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 from 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 

 •' ' ■ ' 11 a few in ' ' i.t of 



M), can ni be- 



' h «>t plants. On sui h a mmI, ' ^ 



■ ■ mid be practised, without fear (>i 



iag the top of the drain.s. The farmer should not, by 

 making his drains shallow, deprive himself of the 

 power to use the subsoil plougn, or other improved 

 imp! * that may l)e invented for the purpose of 

 de« i •• .soil. There are districts in England, 



wh< \e had to be taken up and relaid 



det j ly reason. It would have been an 



actual sttvutg to have laid them deep enough at the 

 first. 



