The size used depends on the length of the drain, the amount of water to carry, the frequency of heavy rainfalls and the character of the soil.

The distance apart varies from twenty-five feet in heavy soils to over two hundred feet in light soils.  The usual depth is about three feet, though the farther apart the deeper they are put.

A lateral tile drain should enter a main at an acute angle to prevent too great a check in the current.

In putting in a drainage system the first thing to be done is to make a plan of the ground and determine the slope of the land and the grade of the drain.  The ditches are then staked out and the digging proceeds.  In digging the ditches plows are sometimes used to throw out the top soil, then the work is finished with spades and shovels.

Professional ditchers use special tools and they take out only sufficient earth to make room for the tiles (Fig. 85).  The tiles are then laid end to end, the joints covered with a piece of sod, some grass, straw, paper or clay, to prevent loose soil sifting in.  As the tiles are laid, enough soil is placed on them to hold them in place until the ditch is filled.

In laying the tiles an even grade should be maintained (Fig. 86).  A lessening of the grade checks the current of water and tends to cause a stoppage of the drain.

The water gets into the drain through the joints where the tiles come together.

The outlet of a tile drain should be protected by brick work or should be of glazed tile such as the so-called terra-cotta tile, to prevent injury by frost.

The mouth of the drain should be protected by a screen of wire to prevent the entrance of rats and other small animals.

GLOSSARY

=Acid=, a chemical name given to many sour substances.

=Albumen=, a nitrogenous organic compound.

=Albuminoid=, a nitrogenous substance resembling albumen.

=Ammonia=, a gas containing nitrogen produced by the decay of organic matter.

=Annual=, a plant that lives only one year; corn and sunflower are examples.

=Anther=, the part of a stamen that bears the pollen.

=Available=, that which can be used.

=Bacteria=, very small plants, so small that they cannot be seen without the aid of a powerful microscope.  They are sometimes called “germs.”  Some of them are beneficial, some do great harm and some produce disease.

=Biennial=, a plant that lives two years, usually producing seeds the second year.

=Bordeaux mixture,= a mixture of copper sulphate, lime and water used to prevent plant diseases.  It was invented in Bordeaux, France.

=Bud=, an undeveloped branch.

=Calyx=, the outermost part of a flower.

=Cambium=, the active growing layer between the bark and the wood of a tree.

=Capillary=, Hair-like.  A name given to very small spaces through which water flows by the force of capillary attraction.