Constructing drains



When the ground is soft and springy the bottom of the drain is laid with bricks placed across. On these, on each side, two bricks are laid flat, one upon the other, forming a drain six inches high and four broad, which is covered with bricks laid flat. Where stones are used instead of bricks, the bottom of the drain should be about eight inches in width, and in all cases the bottom of main drains ought to be sunk four inches below the level of the narrow ones, whose contents they receive, even at the point where the latter fall into them.

The main drains should be kept open or uncovered till the narrow ones are begun from them, after which they may be finished; but before the earth is returned upon the stones or bricks, it is advisable to throw in straw, rushes or brushwood, to increase the freedom of the drain. The small narrow drains should be cut at the distance of sixteen or eighteen feet from each other, and should full into the main drain at very acute angles, to prevent any stoppage. At the point where they fall in, and eight or ten inches above it, they should be made firm with brick or stone. These drains should be eighteen inches wide at the top and sixteen at bottom.

The completest method yet known is to cut the strongest willows, or other aquatic brushwood, into lengths of about twenty inches, and place them alternately in the drain, with one end against one side of the bottom and the other leaning against the opposite side. Having placed the strong wood in this manner, fill up the space between them, on the upper side, with the small brushwood, upon which a few rushes or straw being laid, as before mentioned, the work is done. Willow, alder, asp or beach boughs, are exceedingly durable if put into the drain green, or before the sap is dried; but if they are suffered to become dry, and then laid under ground, a rapid decay is the consequence.

As in some situations it is an object of great importance to save the expense of materials commonly used in filling drains, a variety of devices have, with that view, been adopted. One of these is of the following nature:--A drain is first dug to the necessary depth, narrow at bottom. Into the trench is laid a smooth tree or cylindrical piece of wood, twelve feet long, six inches in diameter at the one end and five at the other, having a ring fastened into the thickest end. After strewing a little sand upon the upper side of the tree, the clay, or toughest part of the contents of the trench, is first thrown in upon it, and after that the remainder of the earth is fully trodden down. By means of the ring, the tree is then drawn out to within a foot or two of the smaller or hinder end; and the same operation is repeated till the whole drain is complete. Such a drain is said to have conducted a small run of water a considerable way under ground for more than twenty years without any sign of failure.





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