Page:The American Cyclopædia (1879) Volume XIII.djvu/202

 192 PAVEMENT gris green when first uncovered. This being scraped off, the portion of the pavement be- neath was found to be a beautiful ruby glass, the color of which^was derived from peroxide of copper, and this by decomposition had be- come converted externally into the green car- bonate of copper. Though the paved roads of the ancient Romans surpass all other structures of the kind that have been made by civilized nations since their time, there are found in Peru remains of works of a similar kind of unknown age, and exceeding them in grandeur and extent. Such were the great roads from Quito to Cuzco, and continued south toward Chili, laid out through mountainous and almost impassable regions for distances variously esti- mated from 1,500 to 2,000 m., and about 20 ft. in breadth. They were built of heavy flags of freestone, and in some parts covered with a bituminous cement, which time has made hard- er than the stone itself. In Mexico, among the ruins of Palenque, are also found pave- ments of large square blocks of stone construct- ed with great skill and nicety. In Europe du- ring the middle ages comparatively little at- tention was given to the paving of streets and roads. Cordova in Spain was paved in 850 by Abderrahman II. Streets in Paris were first paved in 1184 by Philip Augustus. In 1832, in excavating for a sewer in the rue St. Denis, this ancient pavement was met with, and a little below this the still more ancient roadway of gravel of the period of the Roman emperors. There were a few paved streets in England be- fore the time of Henry VII. London was first paved in 1533, but many streets continued in a perilous condition by reason of deep pits and sloughs through the whole of the 16th and 17th centuries. Holborn was paved by royal com- mand in 1417; but the great market of Smith- field remained without pavement 200 years longer. In modern times various methods and materials of paving have been employed. In Holland all the streets are paved with bricks, which are also used for the same purpose in Venice. They obviously lack the strength and durability required for the passage over them of heavy loads. In other cities, instead of the broad flat stones used by the Romans, rounded pebbles called cobble stones, found among the gravel of the diluvium or along sea and river beaches, have been very generally used. These, when of hard stone, closely set, and well ram- med down in a bed of gravel and sand, form an economical and very durable pavement, which gives secure footing to horses and is easily re- paired. Blocks of wood have been at times in some repute, but they have proved objection- able on account of soon becoming slippery, par- ticularly when wet, and also of their tendency to decay. They were commonly cut in hexa- gonal prisms and set upright, so that the wear came across the ends of the grain. Hemlock, being cheap, was usually selected for the pur- pose in America, where however this form of pavement has been generally abandoned. A part of Broadway, New York, between Cham- bers and Warren streets, was laid with hexa- gonal wooden pavement in 1835. Different foundations were tried, such as cobble stones, flagging, and macadam. The surface was coat- ed with tar and gravel. The Nicolson pave- ment was introduced into Boston in 1848, and was among the first wooden pavements exten- sively used. It consists of a foundation of hem- lock, spruce, or pine boards, laid flat upon the ground, upon which blocks of similar wood or of chestnut, from 4 to 6 in. long and wide, and from 2 to 3 in. thick, are set with the grain vertical. Between the blocks, running across the street, inch boards are set on edge, the up- per edge being a little below the surface of the, blocks, and the grooves so formed are filled with coarse gravel. The blocks are either soaked in melted asphalt, or the hot material is turned over the whole and made to fill the interstices. If the blocks and foundation boards were thoroughly kyanized and boiled in the asphalt till saturated, the pavement would un- doubtedly be rendered very durable, especial- ly if a foundation of concrete were first laid. There are other forms of wooden pavement which are held in place by an ingenious lock- ing together, and answer a good purpose as long as the material resists decay. Kyanizing and proper saturating with coal tar or asphalt can always be applied to these pavements ; and conscientious attention to preparing a proper foundation will secure satisfactory results. It may be remarked that honesty in the perform- ance of contracts for paving is an element with- out which no pavement can be expected to have a reasonable degree of permanence. The pavements most common in Europe are ashlar, macadam, concrete both hydraulic and bitumi- nous, and Neufchatel and other asphalt pave- ments. The common ashlar is composed of square blocks of stone, usually granite, about 12 in. deep and 10 or 12 in. long, by 5 to 7 in. wide. A pavement of granite similar to this, though not quite so deep, was some years ago placed in Broadway, New York, called Russ pavement. It proved impracticable on account of slipperiness, and after various attempts to overcome this by cutting grooves, it was re- placed by one made of thinner stones, called the Guidet pavement. In this the stones are 6 or 8 in. deep, and about 12 in. long by 4 in. wide. They are set on edge, and in wearing do not form large smooth surfaces like the ashlar or Russ, and consequently afford greater pro- tection against the horses' slipping. If they were laid upon a concrete foundation, the pave- ment would not need resetting as often as when laid upon common gravel and sand. This pave- ment is now extensively used for the main thoroughfares of cities. Many streets of New York and other American cities have the so- called Belgian pavement, consisting of small cubical blocks, generally of trap rock, which has proved very durable. Cobble-stone pave- ment has been much used in many cities of the