I have not observed any case of obstruction from the roots of our cultivated plants. It has been said by some that the rootlets of mangold will reach the drains under them; and, particularly, where the drains contain most water in rapid motion. I took up the tiles from a drain on this farm, in '54, which had been laid down (by a former occupier), about the year '44, at a depth not exceeding two-and-a-half feet, and not one of these was obstructed in the least degree, although parsnips, carrots, cabbages, mangolds, &c., had been grown on this field. Obstructions may occur through the agency of _mineral_ springs; but very few cases of this nature are met with, at least in this country. I would anticipate this class of obstruction, if from the nature of the land there was reason to expect it, by increasing the fall in the drains and having _traps_ more frequent, where the main outlets are at a distance to render them necessary. In my opinion, the roots of trees are the great intruders to be guarded against, and more particularly the _soft_-wooded sorts, such as poplars, willows, alders, &c. The distance of a drain from a tree ought always to be equal to the height of the latter. _Tiles flattening in the drying process._ With this subject, I am not practically familiar. In most tile-works, the tiles, after passing through the moulding-machine, are placed horizontally on shelves, which rise one above another to any convenient height, on which the tiles are dried by means of heated flues which traverse the sheds where the work is carried on; or they are allowed to dry without artificial heat. I prefer the tiles prepared by the latter method, as, if sufficient time be given them to be well dried, they will burn more equally, and be more durable. The tiles will flatten more or less for the first day or two on the shelves, after which they are _rolled_. This is done by boys (who are provided with pieces of wood of a diameter equal to the bore of the tile when made), who very soon learn to get over a large number daily. The "roller" should have a shouldered handle attached, the whole thickness of which should not be greater than that of the tile. The _shoulder_ is necessary to make the _ends_ of the tiles even, that there may be no _very open_ joints when they are placed in a drain. Once rolled, the tiles are not likely to flatten again, if the operation be performed at the proper time.