Page images
PDF
EPUB

eighteen inches; to be four feet high, two rows of quicksets to be planted on the outward face of the bank towards the field, in the natural soil on the face of the bank."

When a road is formed on a high embankment, a fence may be made according to the following specification :

“ A wall is to be built on each side of the road thirty feet apart, eighteen inches thick at the foundation, and fifteen inches at the top, two feet high above the side channels, and nine inches deep below them ; in all, two feet nine inches.

“ The stones are to be laid in neat level courses, closely jointed and well bonded on both sides, and to be of a kind that will not decompose by the weather.

“ The length of the top stones to be the thickness of the wall, viz. fifteen inches, and from five to six inches deep, to serve as a coping. A mound of earth twenty inches high is to be raised above the wall, with two lines of sods in the front. One row of quicksets, of twelve in each yard, to be planted on the mound. A single rail fence is to be made to protect the quicksets : the top of the rail is to be fourteen inches above the mound."

Whenever a road is carried through a deep

cutting walls should be built for the road fences, if stones can be procured.

Such a fence may be made according to the following specification :

“Walls of dry stone masonry are to be built on each side of the road, thirty feet apart. They are to be three feet above the side channels of the road, and six or nine inches deep below it; they are to be twenty-four inches thick at the foundation, and fifteen inches at the top. They are to batter one inch in a yard on the side next the road, and seven inches and a half in the whole height on the other side. The coping-stones are to be not less than fifteen inches in length at top, to cover the whole thickness of the wall, and to be seven inches thick; neatly hammer-dressed, square-jointed, and set in mortar : the whole of the masonry to be laid in level beds, and well bonded.”

All road fences should be kept as low as possible, in order that they may not intercept the sun and wind, and diminish their effect in producing evaporation.

For this reason, in deep cuttings, the quicks should never be planted at the top of the banks ; but always low down, near the side of the road.

All quick hedges along the sides of roads

should be clipped every year in the months of August or September. They should be trimmed so as to be perfectly level at the top, and with a regular and even surface on the side next the road.

To ensure regularity in the appearance of the hedges, a line and templet should be made use of in trimming them.

CHAP. VII.

ROAD MASONRY.

In constructing roads, masonry is used in a great many cases, and too much pains cannot be taken to have it perfect both in plan and execution.

BRIDGES.

In arranging the plan of a bridge for a road, it should be considered how far it may be made subservient to improve the longitudinal inclination of a road, and save perpendicular height.

When valleys are deep and narrow, they may frequently be passed without great inclinations in the roadway, by selecting a proper position, and building high piers and arches for a bridge, if a stream or river is to be crossed, as is usually the case. On the other hand, when the land on each side of a river is flat, the bridge should be kept low, to avoid an inconvenient ascent to the top of it.

The following are the principal objects, with respect to bridges, which road-makers should have in view, viz. :- 1st, the most eligible situation as regards the direction of the road; 2dly,

the proper width for the roadway; 3dly, the inclinations of the roadway over the bridge; and 4thly, the number and span of the arches.

The best situation for a bridge, as it respects a road, will evidently be that which

preserves

the most direct line: but, for the security of the bridge, it is desirable to have a straight reach above it, and no bend near it.

The width of a bridge between the parapets should be regulated by the nature and quantity of traffic that is to pass over it. On turnpike roads near large towns the width should be at least near forty feet. On turnpike roads in the country thirty or thirty-six feet will be sufficient, and on parish roads, twenty or twentyfour feet.

The inclinations of a road way over a bridge should be very moderate. On turnpike roads they should never exceed one in thirty where it is possible to avoid it, without incurring a great expense in filling for the approaches. The number and span of the arches must depend on various circumstances, which can only be taken into consideration by the engineer on the spot; and even then much more must be left to his experience and judgment than can be derived from any precise rules as to the proper number and size of the arches.

« PreviousContinue »