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inch, to a foot on each side. The dikes are also to be built in mortar between these pilasters.
“ Water wings are to be built into and extended from each abutment for eight feet in length, and to splay back to eight feet apart at their extremities. They are to be founded at the same depth as the abutments, and be carried up to the level of natural ground. A stone pitching to be set between the abutments and water wings; to be set endwise to the streams, and be firmly secured at each extremity. Except the stone pitching, the whole is to be built in good lime and sand mortar. The thickness of the water-wing walls to be the same as specified for the breast walls.”
Specification for a Three-feet Stone Drain.
“ The arch to be hammer-dressed, and the rest of the masonry good sound rubble-work. The abutments must be continued as water wings above and below the arch, for five feet in length, and be splayed back at their extremities. To be founded as low as the abutments, and rise to the springing of the arch. A dry stone pitching to extend under the arch and between the water wings.
Except the pitching, the whole to be set
in good lime and sand mortar up to the level of the roadway. To be the full length of the breadth of the road and dikes. The faces to range with the faces of the breast walls, and the stone dikes to be continued across the arch in the usual manner.”
The water from the side channels of a road should be introduced into the cross drains by side openings or inlets; these should be built with stone masonry, and be ten inches by sixteen inches, and covered with sound flags, at least twenty-six inches long and sixteen inches broad, and two inches and a half in thickness. The top of these covers should be six inches above the level of the sides of the channels, and the whole of the inlet should be built outside of the side channels, as shown in Plate IV.
Inlets may be made along the channels, and covered with iron grates eighteen inches or two feet
square ; the bars of the grates should be three quarters of an inch broad, two inches deep, and one inch apart, if made of cast iron : if the grates are made of wrought iron, it is usual to set the bars in an oak curb; but the cast
metal grates are found to answer better, particularly if bedded in stone or on brick curbing. In some situations it is found necessary to leave an opening or inlet under the footpath, as first described, as well as the grate, to allow the water to get off in thunder-storms: a provision is also sometimes made, in the casting, to allow the grates to be turned up on a hinge, in case of sudden and large runs of water.
Outlets are necessary to receive and carry off the water from the side channels of the road. These outlets may be built of brick or stone: in most cases they may be about one foot square ; when they are for the purpose of carrying the water from the channels into the side drains, on grounds nearly level, they may be made of large six-inch diameter tiles or iron pipes. There should be an outlet at the end of
every cutting, to allow the water that collects in the side drains through the cutting to run off to the side drains before it reaches the embankment. For want of this precaution, embankments frequently suffer very much.
Depôts should be made on the sides of all roads for holding materials for repairing them.
The best form is that which will serve to measure the quantity of materials, as well as to hold them.
The back walls should be twelve yards long, and the two side walls each two yards and a half at the bottom, and to slope at half a right angle to the top: the height of the back and sides should be three feet. A depôt of this form and dimensions will hold twenty-five cubic yards of materials; and four of these depôts on a mile, at 428 yards apart, will contain 100 cubic yards.
The depôts should not in any case be placed farther from each other than a quarter of a mile, so as to admit the materials to be moved in bar
This method of laying them on is better calculated for constant repairs, than drawing them with carts and horses.
Specification for building Depôts of Stone
“ Four depôts are to be built, on each mile of road, in such places as may be pointed out by the engineer or his assistant: they are to be
built with stone and lime; twelve yards long in the clear, three feet high above the side channels of the road, and to be founded as low as necessary below that, to give stability to the work; the ends to be two yards and a half in the clear at the bottom, and to rise to one yard and a half at top; the thickness of the work to be eighteen inches throughout, for the height of three feet; the work under that to be two feet thick. The top of the back, sides, and slopes to be coped with large stones, set on edge, and laid in good mortar.
“ The bottom is to be flagged with sandstone, in the rough, neatly jointed and evenly bedded.
“ The back and ends of the depôts to have a mound of earth thrown up against them, eighteen inches high on the outside, and eighteen inches or two feet on the base, rounded off on the top; and faced with sod if necessary, and the regular quantity of quicksets planted in it, which are to be protected by the field row of posts, and rails before described : a tile drain to be laid in front of the depôt; it is to be thirteen yards long and ten inches in the square.” (See Plate IV. fig. 7.)