An opening of any form, equal to a circle of two or three inches diameter, will be sufficient in most cases, though the necessary size of the duct must, of course, depend on the quantity of water which may be expected to flow in it at the time of the greatest flood.
Whatever the form of the stone drain, care should be taken to make the joints as close as possible, and turf, shavings, straw, tan, or some other material, should be carefully placed over the joints, to prevent the washing in of sand, which is the worst enemy of all drains.
It is not deemed necessary to remark particularly upon the mode of laying large drains for water-courses, with abutments and covering stones, forming a square duct, because it is the mode universally known and practiced. For small drains, in thorough-draining lands, it may, however, be remarked, that this is, perhaps, the most expensive of all modes, because a much greater width of excavation is necessary in order to place in position the two side stones and leave the requisite space between them. That mode of drainage which requires the least excavation and the least carriage of materials, and consequently the least filling up and levelling, is usually the cheapest.
Our conclusion as to stone drains is, that, at present, they may be, in many cases, found useful and economical; and even where tiles are to be procured at present prices stones may well be used, where materials are at hand, for the largest drains.
CHAPTER VI
DRAINAGE WITH TILES.
What are Drain-Tiles?—Forms of Tiles.—Pipes.—Horse-shoe Tiles.—Sole-Tiles—Form of Water-Passage.—Collars and their Use.—Size of Pipes.—Velocity.—Friction.—Discharge of Water through Pipes.—Tables of Capacity.—How Water enters Tiles.—Deep Drains run soonest and longest.—Pressure of Water on Pipes.—Durability of Tile Drains.—Drain-Bricks 100 years old.
WHAT ARE DRAIN-TILES?
This would be an absurd question to place at the head of a division in a work intended for the English public, for tiles are as common in England as bricks, and their forms and uses as familiar to all. But in America, though tiles are used to a considerable extent in some localities, probably not one farmer in one hundred in the whole country ever saw one.
The author has recently received letters of inquiry about the use and cost of tiles, from which it is manifest that the writers have in their mind as tiles, the square bricks with which our grandfathers used to lay their hearths.
In Johnstone's Report to the Board of Agriculture on Elkington's System of Draining, published in England in 1797, the only kind of tiles or clay conduits described or alluded to by him, are what he calls "draining-bricks," of which he gives drawings, which we transfer to our pages precisely as found in the American edition. It will be seen to be as clumsy a contrivance as could well be devised.