36 



differ in their mineral constituents, so do they differ in their 

 retentive powers ; and that while Elkington's system of deep 

 drainage would apply best to one, and Smith's or the Dean- 

 ston system of shallow drainage would apply better to another, 

 there are still innumerable cases where both would be re- 

 jected as inapplicable. Therefore, that course will prove to be 

 the most practical which is based upon a knowledge of the 

 character of the soil in each particular locality. 



LOCATION OF DRAINS. 



The circumstances which develop themselves as the work 

 progresses will go far to determine the precise location of the 

 drains. As a general rule, the principal drains should follow 

 the lowest depressions, the branches running directly down the 

 slopes. Where the ground is nearly level, they should oblique 

 towards the main drain ; and where the ground descends from 

 all points towards a common centre, it would be judicious to 

 run a drain around the edge of the slope to intercept the flow 

 connecting this through the branches with the main drain. 



SIZE OF DRAINS. 



The size of the drains is governed by the probable amount 

 of water which must be carried off. As the volume of water 

 increases by means of the lateral branches, the size of the drains 

 will require to be increased. "Where it is found that the water 

 accumulating, or to accumulate from the different branches, 

 would be greater than could be discharged through the largest 

 sized tiles, a double or even triple row may be laid together in 

 the same trench. 



DEPTH OF DRAINS. 



The depth of the drains is the most important point con- 

 nected with the subject, and one which will require the exer- 

 cise of the most careful judgment. The first care should be 

 to secure a proper outlet, at whatever depth it may be neces- 

 sary to go to obtain it. To this point there must be a con- 

 tinuous descent of at least one foot in eight hundred, unin- 

 terrupted by any depressions, since these would cause an 

 accumulation of deposits, which would in time choke the drains. 



