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by working into a smooth surface often renewed coatings of weak materials. With respect to the subject generally of road materials, it may be observed, that the best descriptions consist of basalt, granite, quartz, syenite, and porphyry rocks.* The whinstones found in different parts of the United Kingdom, Guernsey granite, Mountsorrel, and Hartshill stone of Leicestershire, and the pebbles of Shropshire, Staffordshire, and Warwickshire, are among the best of the stones now commonly in use. The schistus rocks being of a slaty and argillaceous structure, will make smooth roads, but they are rapidly destroyed when wet by the pressure of wheels, and occasion great expense in scraping, and constantly laying on new coatings. Limestone is defective in the same respect. It wears rapidly away when wet, and therefore, when the traffic on a road is very great, it is an expensive material. Sandstone is generally much too weak for the surface of a road, it will never make a hard one.
It is very well adapted to the purpose of a pavement, as a foundation for a road. Flints vary very much in quality as a road material. The hardest of them are nearly as good as the best limestone, but the softer kinds are quickly crushed by the wheels of carriages, and make heavy and dirty roads. Gravel, when it consists of pebbles of the hard sorts of stones, will make a good road, particularly when the pebbles are so large as to admit of their being broken; but when it consists of limestone, sandstone, flint, and other weak stones, it will not ; for it wears so rapidly, that the crust of a road made with it, always consists of a large portion of the earthy matter to which it is reduced. This prevents the gravel from becoming consolidated, and renders a road made with it extremely defective with respect to that perfect hardness which it ought to have.
* For the hardness of some kinds of stone, see Appendix, No. III.
2d. With respect to the quantity of materials to be put on a road in the course of a year, this should be regulated by the traffic on the road and the durability of the materials. The object to be secured, is the giving to the road a sufficient degree of strength to have it at all times smooth and hard. The materials to be provided should be quarried, carted, and broken by contract. The materials when brought in their rough state to the road, should be packed in depôts, or laid up on the wastes, in regular shaped heaps, so as not to interfere with the side channels of the road.
3d. When the materials are stone, they should be broken, as before described for making new
roads, to a size of a cubical form, not exceeding two inches in their largest dimensions.
When gravel is used, the persons who dig it should be required to pass it through sieves before it is carted to the road, so that no gravel pebble, less than one quarter of an inch in diameter, should be carried from the pits to the road.
When the gravel is brought to the road, it should be again sifted by the road labourers, so as to separate the pebbles that are less than three quarters of an inch in diameter from the rest; and all the large pebbles exceeding one inch in diameter should be broken.
4th. The materials, after they have been properly prepared, should be laid on in small quantities at a time: care should be taken to fill up
ruts or hollows as soon as any appear. In those places where the surface of the road has become much worn, a coating of one inch and a half of materials should be laid on : that is to say, a coating only a single stone in thickness, when stones are used; and when gravel is used, a coating not exceeding one inch in thickness. If more materials are necessary, they should be laid on after the first coating is worked in.
The work of repairing roads by laying on new coatings of materials ought to be done between
the months of October and April,' and when the surface of the road is wet. By laying on the materials at this season of the year in thin coatings, they are soon worked into the surface without being crushed into powder, and without producing any great distress to horses drawing carriages over them.
5th. When the funds will admit of it, a road should be divided into districts of four miles each ; and a foreman, with three labourers, should be appointed for each district. The foreman and one or more of the labourers should be daily on the road, taking care that the side channels of the road are kept clean, and making good any injury to the road as soon as it appears.
The foreman should work with the men : he should take care that the orders of the surveyor are attended to, and be able to measure road work.
A regular plan should be arranged, and strictly adhered to, for keeping the water channels and drains of a road always open, and free from dirt.
In the month of October in each year, every water channel and drain should undergo a general repair, and be cleared of all deposited earth and weeds.
At the same time, the surface of the whole road should be scraped, all ruts and hollows
should be carefully filled with materials, and all weak parts of the surface coated with materials; that is to say, the road should be put in every respect into a complete state of repair, so as to preserve it from being broken up during the approaching winter.
A road should be scraped from time to time, so as never to have half an inch of mud upon it; this is particularly necessary to be attended to, when the materials are weak; for if the surface is not kept clean, so as to admit of its becoming dry in the intervals between showers of rain, it will be rapidly worn away.
The road men should scrape from the centre to the sides; the mud should not be scraped into or allowed to remain in the channels, as is too frequently the case; but put into small heaps, about one foot from the side channels, so as not to stop the running of water in them.
These heaps should always be removed, the moment the mud is sufficiently dry to admit of its being put into carts or barrows.
The scrapings should never be laid in heaps on the wastes or footpaths; they should be spread evenly over the hollow parts of the wastes, till the wastes are brought to a regular surface; afterwards they should be carted at once off the road to some convenient place