THE DRAINAGE OF THE FARM. 4(35 



may find that drain pipes filled with air, being lighter than soil, will have 

 a tendency to rise towards the surface. Whatever the cause may be, the 

 fact requires no proof, that after ten or twelve years, drains are found to 

 be G or 7 inches shallower than when they were formed. And as drain- 

 age is generally intended to be a permanent improvement ; as deep drains 

 permit a greater depth of soil and subsoil to be exposed to the action of 

 the air than is possible with shallow drainage; and as a much deeper and 

 more effective system of cultivation than that presently in use is advis- 

 able in many instances ; from all of these reasons, as well as others that 

 niiu'ht be stated, I hold that drains should be made as nearly 4 feet deep 

 as possible. 



There are various circumstances, no doubt, which ought to modify in 

 practice any general rule of this kind. Perhaps it is impossible, except at 

 an enormous expense, to get an outfall sufficiently deep to admit of the 

 drains being made 4 feet. And, in other cases, an immediate return on a 

 v moderate outlay may be wished ; and for this purpose, shallow or 

 30-inch drains will be preferable. In some instances, particularly in very 

 dense tenacious soils, it may be advisable to put in only 3 feet drains. 

 The drainage lines must be kept so near to each other, in order to lay land 

 of this kind dry, that the workmanship connected with 4 feet drains be- 

 comes very heavy by the acre. To obviate this evil, there is no alternative 

 lut that of reducing the depth, and bringing the drains a little closer 

 together. If this is done in a skilful way, the drainage will prove per- 

 fectly effective, though scarcely so complete as it would have been with 4 

 feet drains having the same, or very little greater, distances between 



Ml. 



Far greater errors have been committed in regard to the distances apart 

 of drains than as respects their depth, 



ftules applicable to every oaae cannot be laid down; but I can state 



nil principles, in reference to the distances at which drains should he 

 I -laced in soils having specific characters. In very close clays, for 



ami ; t drains should be from 18 to 25 feet apart. It' tin- depth is 

 ; hy U inches, 18 to 21 feet will he wide enough. Then, on i< 



'ill rather tenacious land, 25 to 30 feet intervals do very 

 !, when the depth is tour feet ; and on V.TV porous soils, 40 to .">< : 

 and ill greater width-, will he sutli<-ient. In many instances, a | 



will remove the injurious spring or 



nt of land. The piece of ground to be operated upon in 

 this vprcial . tly re.pi refill in-p.vt ion, and to be treated ac- 



DD 



