116 
Oh Drainiiifj Running Sands. 
larger quantity of water is cut into, which is about 3 inches in 
thickness ; beneath it lies the marly clay upon which we generally 
lay the tiles. But it sometimes happens that on the higher parts 
of the field the clay referred to cannot be reached, on account 
of the increased thickness of the sand. Still when this is the 
case, the sand beneath the stratum of water, on account of its 
elevation, is of a firmer and drier kind, upon which we can with 
confidence place the tiles, never having found them to fail when 
a rapid descent was avoided. To reach the clay in every place 
is not practicable. The average depth of the drains is about 
3 J feet. 
The manner in which the work is done is as follows : — The first 
object is to ascertain the depth at which the bottom water lodges. 
If deep, and the earth very porous, the drains are set out much 
farther apart than when it lies near the surface. Thus they are 
varied in their distance from each other in proportion as the water 
lies deep or otherwise ; that is to say, when we can cut to a depth 
of 4 feet in that which is entirely porous, the drains are set 15 
yards apart, and when we find the water to lie as deep as 6 feet, 
their relative distance is 20 yards. But when the clay lies near 
the surface, being only about 12 inches beneath it in some in- 
stances, they are set out only 8 yards apart. 
Having ascertained the proper depth and relative distances of 
the drains, the outlet is next attended to, a point which is fre- 
quently too slightly regarded, and consequently often proves in- 
jurious, and sometimes entirely ruinous to the whole work. When 
this is accomplished, the drains are set out as above. The land, 
which is very undulating, is cut to a certain level depth through- 
out, so as to give a gradual and proper descent towards the out- 
let, and so deep as to only require two draws or spits to be taken 
out afterwards. The earth at the top being thus removed, the 
level is then used (as from the porousness of the land no water 
by which the descent might be taken, runs so near the surface), 
and the greatest care is taken at this stage of the work to have 
all thoroughly true, and the descent given that is required, as the 
finishing depth and the fall are ruled by the top levelling, before 
the two s])its referred to are taken out. To cut the drains deeper 
before using the level would be to render the use of it almost 
impracticable. 
All is now ready for completing the work, tiles and bottoms 
being laid by the side of the drain, and three men engaged in 
the work ; two of the most experienced to cut the drain to its 
proper depth, the one following the other in as short a space as 
possible, and the third immediately following with the bottoms 
and covering. The main drains are laid either with large-sized 
tiles and bottoms, or with two common ones, one upon the other. 
