The method which this gentleman pursues in con structing his main drains is stated by him to be the fol lowing : When the ground is soft and spongy, the bot tom 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.—When the bottom of the trench is found to be a firm and solid body ; such as clay or marl, he formerly thought that it might not be necessary to lay the bottom with brick ; but in this lie has candidly acknowledged that he was quite wrong. By the runs of water, the alternate changes from wet to dry, and the access of air, these hard bot toms were rendered friable, crumbled away, and allowed the drains to fall in and to choke up, that were not sup ported by a bottom laid with brick or stone. When stones are used instead of bricks, Mr Bayley thinks that 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 nar row 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 16 or 18 feet from each other, and should fall into the main drain at very acute angles, to prevent any stoppage. At the point where they fall in, and 8 10 inches above it, they should be made firm with brick or stone. These drains should be 18 incites wide at the top, and 16 at bottom.
A mode of draining clay soils wet by rain or surface water, practised by the late Sir Henry Fletcher, Bart. with great success, seems worthy of being stated. The upper soil is of good quality ; but, being situated in a mountainous part of the country, the frequent rains kept it so full or water, that it produced only a coarse grass, worth 3s. per acre. The inferior soil of clay was of great depth. The mode of draining which has been practised upon it is the following :—On grass lands he digs 22 inches, or 2 feet deep ; the first spadeful is of the turf, taken so deep, as where it separates from the clay, the turf is dug carefully out and preserved unbroken with its grass side up, and laid on one side of the cut ; then, with a very strong spade, 18 inches long, 6 inches wide at top, and 2 at the bottom, he digs a spadeful in the clay, which the men spread about the land, on the side of the drain opposite to where the turfs were laid, as far as possible from the drain, so that none may get in again. A scoop follows to clear out the fragments in
the bottom, which are also spread in like manner. They are then ready for filling ; and, in doing this, he takes three stones of a thin flat form, two of which are placed against the sides of the drain, meeting at bottom ; and the third caps the other two. Thus, a hollow triangular space is left to convey the water, which is subject to no accidents that can fill it up, or impede the current. Stones alway sink deeper in the ground ; and in the common method, this f•equently causes stoppages, by their being partly buried in the clay ; but the triangle, when it subsides, does it regularly, and keeps its form and the passage for the water clear. One cart-load of stones in this way, will do a considerable length of drain. They arc carefully laid down by the side of the cut, with a shovel or basket ; and if there are any small refuse stones left on the ground after the drain is set, they are thrown in above. The stones being thus fixed, the sods are then trimmed to the shape of the drain, and laid on them with the grass side downwards, and none of the clay used in filling up.
Not only stones and bricks, but also wood and other materials have been used for filling drains. Upon this point, Lord Petre expresses himself thus : " The drains tilled with wood, and covered as usual with straw or rushes, arc preferable to stones or any other kind of materials ; for as the wood decays, the water continues to pass. AVhen filled with stones, and the drains stopt up, which must be expected to take place in time, the earth becomes quite solid round the stones, and as they do not decay, the filtering of the water is for ever ob structed. But this is not the case when bushes or wood are used; continual filtering and draining are then for ever to be perceived ; and, by repeating the operation a second time, cutting the drains transversely of the old ones, the benefit of the filtering-s through the rotten wood is secured, and the spewing up of old, broken, and damaged drains, corrected and carried off. Besides, as bushes form a much greater number of cavities than either stones or poles, they are less liable to stop up, and encourage filtering more than large and more solid bo dies. A load of bushes containing 1.20 faggots, will do about 360 rods ; and a load of straw containing 120 bot tles the same ; the load of bushes is generally worth about 1•1s. and the straw 18s. per load. I therefore calculate this expense about I 2s. per acre, ditches a rod apart.