DRAINAGE OF SOILS. 
329 
vents the surface water from getting into the drain_its weight causes 
the sides to fall in—makes it more difficult to scour or clean it—and 
adds much to its disagreeable appearance in the middle of a field. In 
cases where the augur or wells are obliged to be resorted to in open 
drains, they should never be made in the bottom, but on one side, 
with the outlet eight or ten inches above, which will prevent surface 
or flood water depositing any sand or sediment in the bore-holes 
whereby they might be injured. 
Shoulder Drains .—Any surface water or partial springs in moss 
and marshy grounds, on which the large drains have no effect, and 
where stones cannot be used on account of the softness of the soil, is 
most effectually remove d by means of shoulder drains. The method 
of making them, is by digging a trench from fourteen to sixteen 
inches wide, the sides perpendicular to the depth of two or three feet, 
and then by taking out the last spit with a spade, the breadth of 
which is three inches at the bottom, and four or five at the upper 
part. A shoulder is left on each side, on which the sod that was first 
taken up is carefully laid with the grass side downwards, or if it is not 
strong enough, others must be cut in the vicinity, and the remaining 
space filled with the loose earth a few inches above the level of the 
surface of the adjacent ground. Drains of this description, when 
properly executed and moles kept out of them, will operate for a great 
number of years. 
Covered Drains .—In every instance where covered drains are used, 
their dimensions depend on the depth, the quantity of water they 
have to carry, and the kind of materials they are filled with. When 
the depth does not exceed five feet, two feet wide at top will be suf¬ 
ficient, but whenever it is more, the width should be increased four 
inches for every foot in depth, and the width at the bottom should be 
twenty inches which will give a sufficient space to build a substantial 
conduit. When this is not attended to, and the bottom of the drain 
is made so narrow that the stones of which the sides of the conduit 
are formed are obliged to be set on their edges, and the covers laid 
on them in this insecure state, they, in many instances, fall down be¬ 
fore the drain is half finished, causing it to burst in a very few years, 
and often forming springs in the driest part of the field. 
In digging drains, there are several circumstances which, if at¬ 
tended to, will greatly facilitate the execution of the operations, such 
as having the stones laid down by the upper side of the lines of the 
drains before the work is commenced, to be ready in case the sides 
should slip or fall in, which often happen in mixed soils, as, when 
this precaution is not attended to, the expense is not only consider- 
