5S-2 R A R A ROACH (Leuciscw rutilus), a fish of the family of Carps (Cyprinidae.) and of the genus Leuciscus, which comprises also the Rudd, Chub, and Dace. It is one of the most common freshwater fishes of Europe north of the Alps, and extends northwards as far as Lapland. Its pharyngeal teeth are in a single series, five or six on each side. The body is generally rather deep, its greatest depth being about one-third of the total length, the caudal fin not included. The scales are large, from forty-two to forty- four along the lateral line, seven or eight series being above it, and three between the lateral line and ventral fin. The first dorsal rays are inserted vertically above, but not in advance of the root of the ventral fin. The anal fin is supported by from twelve to fourteen rays. The general colour is silvery, in adult fishes with a red tinge about the lower fins. Roach spawn from April to May, and frequently produce hybrids with other allied fishes, such as the rudd and the bream. They never attain to a large size, a roach of 1 ft> being considered an unusually large fish. As a food-fish this species is not held in esteem ; but by the pleasure it affords to a large class of humble anglers it rivals any of the freshwater fishes which give more pretentious sport, and has properly been made the subject of a special work, Tlie Book of the Roach, by Greville Fennell (London, 1870). ROADS AND STREETS. The earliest roads about which anything definite is known are those of ancient >man Rome, one of the oldest of which and the most celebrated ids. f or the grandeur of its works the Appian Way was com- menced in 312 B.C. Roman roads are remarkable for pre- serving a straight course from point to point regardless of obstacles which might have been easily avoided. They appear to have been often laid out in a line with some pro- minent landmark, and their general straightness is perhaps due to convenience in setting them out. In solidity of construction they have never been excelled, and many of them still remain, often forming the foundation of a more modern road, and in some instances constituting the road surface now used. It is consequently possible, with the help of allusions of ancient writers, to follow the mode of construction. Two parallel trenches were first cut to mark the breadth of the road ; loose earth was removed until a solid foundation was reached ; and it was replaced by proper material consolidated by ramming, or other means were taken to form a solid foundation for the body of the road. This appears as a rule to have been composed of four layers, generally of local materials, though sometimes they were brought from considerable distances. The lowest layer consisted of two or three courses of flat stones, or, when these were not obtainable, of other stones, generally laid in mortar ; the second layer was composed of rubble masonry of smaller stones, or a coarse concrete ; the third of a finer concrete, on which was laid a pavement of poly- gonal blocks of hard stone jointed with the greatest nicety. The four layers are found to be often 3 feet or more in thickness, but the two lowest were dispensed with on rock. The paved part of a great road appears to have been about 16 feet wide, and on either side, and separated from it by raised stone causeways, were unpaved side-ways, each of half the width of the paved road. Where, as on many roads, the surface was not paved, it was made of hard concrete, or pebbles or flints set in mortar. Sometimes clay and marl were used instead of mortar, and it would seem that where inferior materials were used the road was made higher above the ground and rounder in cross section. Streets were paved with large polygonal blocks laid as above described and footways with rectangular slabs. Specimens are still to be seen in Rome and Pompeii. There are no traces of Roman influence in the later roads in England, but in France the Roman method appears to have been followed to some extent when new roads were constructed about the beginning of the 18th century. A foundation of stones on the flat was laid, and over that two layers of considerable thickness, of larger and smaller stones, bordered by large stones on edge, which appeared on the surface of the road. In 1764 Tresaguet set the foundation-stones on edge and reduced the thickness of the upper layers, and his method was generally followed until the influence of Macadam began to be felt. A French chaussee with accotements still retains, some resemblance to the old Roman roads. The almost incredibly bad state of the roads in England English towards the latter part of the 17th century appears from roa(l3 > the accounts cited by Macau lay (Hist., c. iii.). It was due J^.* chiefly to the state of the law, which compelled each parish to maintain its own roads by statute labour, but the estab- lishment of turnpike trusts and the maintenance of roads by tolls do not appear to have effected any great improve- ment. At the time of Arthur Young's six months' tour in 1770 the roads would seem to have been almost as bad as ever, and it is doubtful if there was much improvement up to the beginning of the present century. The turnpike roads were generally managed by ignorant and incompetent men until Telford and Macadam brought scientific prin- ciples and regular system to their construction and repair. The name of Telford is associated with a pitched foundation, which he did not always use, but which closely resembled that which had been long in use in France, and the name of Macadam often characterizes roads on which all his precepts are disregarded. Both insisted on thorough drainage and on the use of carefully prepared materials, and adopted a uniform cross section of moderate curvature instead of the exaggerated roundness given before; but, while Telford paid particular attention to a foundation for the broken stone, Macadam disregarded it, contending that the subsoil, however bad, would carry any weight if made dry by drainage and kept dry by an impervious covering. Macadam was engaged more with the repair of old roads than with the construction of new ones, and, though it is not possible to agree with all his doctrines, the improve- ment which he effected in road management and main- tenance was great and lasting. Construction of Roads. A- road should be as short as possible CON- between two points to be connected, but straightness must often STHUC- be sacrificed to avoid difficulties and expense and to secure good TIONC- , gradients. The latter should be as easy as practicable, having re- ROADS gard to the country to be traversed, and it is desirable that there Gradie should be a ruling gradient than which none should be stci-pcr. On a level macadamized road in ordinary repair the force which the horse has to put forth to draw a load may be taken as one- thirtieth of the load. But in going uphill the horse has also to lift the load, and the additional force to be put forth on this account is very nearly equal to the load drawn divided by the rate of gradient. Thus on a gradient of 1 in 30 the force spent in lifting is one-thirtieth of the load, and in ascending a horse has to exert twice the force required to draw the load on a level. In de- scending, on the other hand, on such a gradient, the vehicle, when once started, would just move of itself without pressing on the horse. A horse can without difficulty exert twice his usual force for a time, and can therefore ascend gradients of 1 in 30 on a mac- adamized surface without sensible diminution of speed, and can trot freely down them. These considerations have led to 1 in 30 being generally considered as the ruling gradient to be aimed at on first- class roads, though 1 in 40 has been advocated. Telford adopted 1 in 30 as the ruling gradient on the Holyhead road through North Wales, and there are only two gradients steeper, in places where they were unavoidable. All unnecessary rises and falls should be avoided, but a dead level is unfavourable for drainage, and on this account 1 in 100 to 1 in 150 is the flattest gradient that is desirable. Such slight rises and falls are probably rather favourable than other- wise to ease of draught by horses. In transverse section, roads in the United Kingdom generally Cross comprise the carriage- way, a space on each side, on one or both of sectioi which there may be a footpath, then the fences, and outside all the ditches. The width of the carriage-way may be from 15 feet, which allows of the easy passage of two vehicles, to 30 or 50 feet
