(6.) All loose stones should be picked off at once or put together in hollow places upon the roadway, as, if allowed to remain, they are not only dangerous to horses, but are liable to be crushed, or to be forced through the skin of the roadway, thus causing it damage.
(7.) Water lodging upon a road does great mischief, but it should not be let off by digging a trench with a pickaxe to the side of roadway, as is sometimes done.
(8.) A roadway when very dry sometimes suffers through disintegration of the surface.
(9.) Scraping the mud off a roadway may damage it by loosening stones; sweeping the surface when wet is best.
(10.) A heavy shower does a road good by washing it; a continuous drizzle, especially after frost, is very ruinous to a roadway.
(11.) A good cleansing is sometimes worth a coat of metal.[25]
Bituminous Roadways.
In some towns in England bituminous or asphalte macadamised roadways are made. This consists in mixing ordinary coal tar with the road metal ordinarily employed for macadamised roads, only it must be borne in mind that the metal employed must be limestone or some other soft material, otherwise it will not wear down evenly with the tar, and thus a lumpy surface will be produced in course of time.
The method of mixing is by heating the stone, which has of course been previously broken to the required size, and then thoroughly mixing and incorporating it with the tar. This is then carried to the roadway, is spread in the ordinary manner and well rolled to the proper contour, a surface being afterwards given to it by a coating of about 2 inches thick, composed of a similar mixture, the stones of which are of much smaller size.
Another method is to place about 6 inches of the broken metal described above upon the necessary foundation. Upon this a boiling mixture composed of about 50 gallons of creosote oil and 1 ton of pitch is poured until every interstice is filled with the mixture. Whilst this is still warm, a thin layer of small broken stone is spread upon the surface and well rolled; more small stones or chippings are added, and the whole is rolled until the surface of the roadway has attained its proper contour and presents a perfectly smooth and clean appearance, little inferior to that of real asphalte.