d is over-drained, should be
suspended until the soil has acquired compactness by its own weight, and
by the ameliorating effect of culture and the elements.

Mr. Denton, alluding to the opinion of "many intelligent men, that low
meadow-land should be treated differently to upland pasture, and upland
pasture differently to arable land," says, "My own observations bring me
to the conclusion, that it is not possible to lay pasture-land too dry;
for I have invariably remarked, during the recent dry Summer and Autumn
particularly, that both in lowland meadows, and upland pastures, those
lands which have been most thoroughly drained by deep and frequent
drains, are those that have preserved the freshest and most profitable
herbage."

While, therefore, we have much doubt whether any land, high or low, can
be over-drained for general cultivation, it is probable that a less
expensive mode of drainage may be sometimes expedient for grass alone.

While we believe that, in general, even peat soils may be safely drained
to the same depth with other soil, there seems to be a well-founded
opinion that they may frequently be rendered productive by a less
thorough system.

The only safety for us, is in careful experiment with our own lands,
which vary so much in character and location, that no precise rules can
be prescribed for their treatment.

CHAPTER XVIII.

OBSTRUCTION OF DRAINS.

Tiles will fill up, unless well laid.--Obstruction by Sand or
Silt.--Obstructions at the Outlet from Frogs, Moles, Action of
Frost, and Cattle.--Obstruction by Roots.--Willow, Ash, &c., Trees
capricious.--Roots enter Perennial Streams.--Obstruction by Mangold
Wurtzel.--Obstruction by Per-Oxide of Iron.--How
Prevented--Obstruction by the Joints Filling.--No Danger with
Two-Inch Pipes.--Water through the Pores.--Collars.--How to Detect
Obstructions.

But won't these tiles get filled up and stopped? asks almost every
inquirer on the subject of tile draining.

Certainly, they will, if not laid with great care, and with all proper
precautions against obstructions. It cannot be too often repeated, that
tile-drainage requires science, and knowledge, and skill, as well as
money; and no man should go into it blindfold, or with faith in his
innate perceptions of right. If he does, his education will be
expensive.

It is proposed to mention all the various modes by which tiles have been
known to be obstr