Open Drains.— The rudest forms of open drains are the deep furrows, lying between nar row highbacked ridges which are still to be found in some parts of the country with their accompanying water-furrows (egawa furrows or ((gripe) for discharging their streams. These are only meant to carry off the surplus water after the soil is completely saturated. In doing so, however, they carry along with it all the best portions of the soil and of the manure which may have been spread upon its surface.
Open Drains as Water-courses.—The ordi nary ditch (dike) is the common form of this kind of drain, which, though necessary to a certain extent, ought, nevertheless, to be spar ingly seen where a perfect system of drainage has been effected. They are constant sources of annoyance and expense from their sides crumbling in, the numerous weeds which they harbor and the thorough scouring which ffiey require every year. Open ditches occupy an im portant place in the early stages of draining bogs ; but after the bog has become consolidated the greater portion of them may be dispensed with and their places supplied by large covered drains.
Open Drains for Collecting Water from the Land through which they pass (Sheep. These are employed in drying the surface of mountain pastures, where a more ex pensive and perfect system of drainage would not yield an adequate return for the outlay. They consist of trenches of 12 or 16 inches in depth and 18 in width, placed so as to intercept all the water which may flow from portions of land above them. They are opened at intervals in a direction nearly transverse to the line of the greatest slope and should have sufficient inclination to keep tbe water flowing toward the mains or leaders. These latter should be cut in the hollows or in such other places as will per mit the small drains or feeders to empty them selves most readly into them, and be made to discharge into the nearest water-courses.
Covered Drains.— We now come to the consideration of the more important description of drainage— the removal of water by means of covered drains. The simplest of all the forms of these are what are called mole-drains, and they are formed by means of a machine called the mole-plough. This machine consists of a wrought-iron frame on four wheels, the front pair being connected with worm and chain steer age. A coulter with pointed sock, capable of being raised and lowered to regulate the depth of the drain, is attached to the frame. The "mole,") an oval piece of iron three and one-half inches in diameter, follows the sock, to which it is attached by a short chain. The track which the mole leaves in the ground is the water chan nel. This machine is dragged through the soft clay, which is the only kmd of land on which it can be used with propriety, by means of a windlass on the fore end of the frame and a double length of wire-rope wound by an engine on the higher part of the field. A team of horses
returns it to the lower side, out of work.
Wedge-drain.—The wedge-drain, like the mole-drain, is merely a channel formed in the subsoil, and, like it, can only be used in pasture lands. In forming wedge-drains, the first spit, with the turf attached, is laid on one side, and the earth removed from the remainder of the trench is laid on the other. The last spade that is used is very narrow, and tapers rapidly, so as to form a narrow wedge-shaped cavity for the bOttom of the trench. The turf first removed is then cut into a wedge, so much larger than the size of the lower part of the drain that, when rammed into it with the grassy side undermost, it leaves a vacant space somewhat triangular in shape in the bottom of six or eight inches in depth.
Permanent drains are of two kinds, stone and tile drains.
Stone-drains.— These are either formed on the plan of open culverts of various forms, or of small stones in sufficient quantity to permit a free and speedy filtration of the water through them. As a specimen of the former of these, we may instance the box-drain, which is formed of flat stones neatly arranged in the bottom of the trench. The largest and flattest stones are used in laying the bottom and for covers; the smaller ones are placed on the sides, the whole forming an open tube. The second description of stone-drains, generally known as the broken stone or rubble drain, is not so thoroughly ef fective as the first.
TileArains or Sewer-pipe' drain:L-0f all the materials which have yet been brought for ward for forming the conduits of drains, none are so well fitted for the purpose as tiles or pipes of burnt clay. Draining tiles, especially those in the form of pipes, possess all the qualities which are required in the formation of drains, affording a free ingress to water, while they effectually exclude vermin, earth, and other in jurious substances. When first introduced they were of clumsy construction, and being hand made, sold at a high price. They are now made of ordinary clay and vitrified clay to resist the moisture, and also of concrete. The vitrified are most durable but the concrete or cement pipe is largely used; the best form appears to be the cylinder. Good pipes are straight, smooth and free from flaws, and when struck should ring clearly. Durability is shown if the wet pipe will dry quickly before a hot fire without crumbling. Where a sudden descent occurs in the course of a drain, or where there is a run ning sand or a boggy place, pipes of one size should either be entirely sheathed in larger ones, or they should be furnished with collars. These collars are merely short sections of pipes of such a size as to fit upon smaller ones, by which means the smaller ones may be so joined end to end as to prevent them from slipping down past each other.