45 
inches in diameter. The bed of the trench should be smooth, firm, 
and even; the inclination of no drain should be less than half an 
inch or more than eight inches per chain. 
The direction of the main drain should first be settled, and the 
minor drains are then mapped out in such a manner that the un- 
dulations of the surface are taken due advantage of in the way of 
securing a free and easy descent of the water. They should be 
placed midway between the rows of trees and, if possible, parallel 
with the fall, and lead into the main open drain that follows the 
natural watercourse. Laid on sand they are not so liable to become 
displaced. Great care must be taken that, though the surface be 
undulating, the pipe-bed has a uniform and even descent, and that 
there are no depressions in it where the water could lodge, eventually 
decomposing the pipes and filling up the drains with sediment. The 
depth of the main always exceeds by a few inches the depth of the 
laterals, which should be laid in a direction generally perpendicular 
to it, althouugh where they enter the main drain that direction should 
be at an easy angle. These lateral drains, when laid fish-bone 
fashion on either side of the main drain, should not enter it im- 
mediately opposite, but should alternate to fit and adjust two pipes. 
The smaller one is chipped at one end, flute-shape, whilst a hole is 
knocked out of the larger pipe to receive it. The last pipe, at the 
outlet, is of iron, and its end is well grated to guard against the 
intrusion of vermin, whilst each of the minor pipes is also protected 
where it springs, to prevent earth and silt finding its way inside the 
drain and blocking it. Should a stoppage occur, an excavation is 
made and the cause, whatever be its natuie—displacement of tile, 
accumulation of silt, or roots of trees—-removed. A correct plan of 
the deep-drainage system is in every case necessary for future use. 
The following table gives, for thé character of the soil it is 
intended to drain, the distance apart the drain is generally set, the 
depth from the surface, and the number of 12-inch-long tiles re- 
quired to the acre:— 
: 
Soil. erry ae aa ee 
in feet. feet. required, 
Stiff clay ase een 15 3 2,804 
Friable clay ... sie 18 3 2,420 
Strong loam ... ies 21 3 | 2,074 
Gravelly loam at 30 3 | 1,452 
Light loam ... bis 33 36 1,320 
Sandy loam ... ain 40 3-6 | 1,089 
