ROADS. 



355 



HoacU ad undulating surface. Attention should alto be paid to 

 Highway*, ^jj t ne ditches of a moderate depth, us the tenacity of 

 """"Y^"" such soils depends upon their being kept in a some- 

 what moist state. If a section of such ground be expos- 

 ed to the sun and air, by deep side cutting, it soon pul- 

 verizes, and loses its elasticity, when the level of the 

 ro<l fulls, and its surface gets into disorder. The 

 drainage of a road should rather be made across than 

 in a lateral direction, as being less apt to be injured by 

 the traffic upon it. Whatever degree of convexity 

 is given to the cross section of the surface of the 

 road, the same figure should be given to the bed or 

 ground on which the broken stones are to be laid. By 

 this means the drainage will be assisted, and the metal 

 preserved of an equal depth throughout, instead of be- 

 ing thicker in the middle, or under the horse path, 

 than where the carriage wheels travel. By this means 

 also a considerable portion of metal will be saved, espe- 

 cially in situations where it is laid of the whole breadth 

 between the side drains. This is further illustrated by 

 Fig. 4, Plate CCCCLXXX. and its description at the 

 end of this article. 



The curve, or top line of the cross section of the road, 

 is also important, and its degree of convexity should 

 be regulated very much by the line of draught, the 

 principal object being to carry off the moisture by sur- 

 face drainage. But, for this purpose, the declivity from 

 the centre to the sides may be very gentle, it being 

 only wanted to take it off so easily as not to endanger 

 the washing of the pulverized stuff entirely away or rut- 

 ting the surface. To provide for the rain-water flow- 

 ing in direct lines from the centre to the sides of the 

 road, would be to barrel or round it too much, as was 

 the case formerly, even to a degree that was dangerous 

 for carriages. The cross-section of a level track of 

 road should be elliptical, falling from the centre to the 

 verges on either side, at a rate not exceeding an inch 

 and a half perpendicular to a yard horizontal. But 

 where an acclivity in the line of draught occurs, where 

 carriages are in the greatest danger of being upset, the 

 surface of the road should be kept flat, or with a fall 

 not exceeding three quarters of an inch to the yard, to 

 take the water gently off toward the sides, and prevent 

 it, during heavy rains, from rutting the road in a la- 

 teral direction. 



Breadth of It has been complained that many thousand acres 

 the road, of land throughout the kingdom are lost to the agri- 

 culturist, from the increased breadth which is now 

 given to our public roads ; but this, to say the least, 

 is a very narrow view of legislative policy. Inde- 

 pendently of the safety and conveniency of the traf- 

 fic, the mere consideration of drying the road by 

 more speedy evaporation is a sufficient reason for pre- 

 serving a spacious breadth in the formation of all roads, 

 while the effects of the rising growth of the hedge- 

 rows, and the ultimate erection of buildings along it 

 will be rendered less injurious. The highways or great 

 lines of road should, in no instance, be formed of a less 

 breadth than forty feet, and the metal bed not less 

 than eighteen feet broad, with at least one footpath of 

 five feet in breadth along the side ; especially within a 

 few miles of all towns and villages. It would be diffi- 

 cult to give any scale of breadths for public roads, the 

 local circumstances of which vary so much. But, with- 

 out presuming to be fastidious, we notice, that, within 

 six or eight miles of all large cities or towns, the ap- 

 proaches should not be formed at less than sixty feet be* 

 tween the fences. In such situations the whole breadth 



hould b metalled, or laid with broken stones. In Road* tad 

 the vicinity of towns of about 50,000 inhabitants, the Highway*, 

 breadth should be at least fifty feet between the fences, "Y"""^ 

 and be in like manner metalled from side to side. 

 Where the population does not exceed 20,000, the sta- 

 tutory breadth of forty feet msy be adopted, the metal, 

 ling being still continued of the whole breadth, with 

 paved side-drains. At intermediate distances, where 

 it is not thought advisable to have the metal of a 

 greater breadth than eighteen feet, the compartments 

 between the metal bed and the side-drains may be laid 

 with gravel or chips of stone to the depth of not lest 

 than half the thickness of the central part of the road. 

 In the vicinity of London, and the capitals of Dublin 

 and Edinburgh, and other great towns, as Glasgow, 

 Manchester, Liverpool, &c. it would be desirable that 

 the principal approaches were at least seventy feet in 

 breadth, fully metalled between the side-drains, which 

 ought to be neatly formed, and paved, and the roads 

 provided with a foot-path on each side. 



By the fabric of the road is more particularly meant, Fabric of 

 the component parts of the metal bed. Where the the road, 

 bottom is naturally wet and spongy, it is well to ram 

 it with chips of stone or with rubbish somewhat freed 

 from earthy particles. It is extremely desirable, in every 

 situation, that the road-metal should be broken to a 

 uniform size, so as to form a compact body throughout. 

 But, as the preparation of the small metal suitable for 

 the surface of a road is expensive, it will, in many 

 situations be found advisable to a lay a stratum or 

 course of hand-laid stones, of from five to seven inches 

 in depth, with their broadest ends placed downwards, 

 and the whole built compactly together, upon the pre- 

 pared bed or soil. On this course of stones, broken 

 metal to the depth of not less than eight inches may 

 be laid, though the quality of the rock should be kept 

 in view in fixing the depth of this upper stratum. 

 In fixing upon the size of the top metal, the more hard 

 and tough its nature is, the smaller it may be broken ; 

 it being an object of main importance to have the me- 

 tal " well assembled," as the road-makers express it, 

 or broken of a uniform size. In almost every county 

 there is a variation in the quality of the rock, and also 

 in the size to which it is broken. Roads have latterly 

 been made under a specification a? to the weight of the 

 pieces, varying from six to eight ounces. Formerly it 

 was not uncommon to have them specified, of the 

 size of a " hen's egg," or even of" a roan's fist." By 

 reference to weight, the road-maker's operations became 

 more precise ; but regard should also be had to the 

 specific gravity of the materials, which differs con- 

 siderably. For example, granite may be taken at 

 twelve cubic feet in the ton, and whinstone (the green- 

 stone, basalt, and clinkstone of mineralogists) is often 

 met with of similar weight. Compact limestone and 

 flint are about fourteen, and quartzy sandstone about 

 fifteen feet to the ton. Perhaps the most convenient 

 and uniform test for the size of road-metal is a ring 

 measuring two inches and a half diameter in the void. 

 When the metal is thus broken, and the road care- 

 fully treated, its surface soon becomes smooth and 

 compact, without requiring the addition of blinding, 

 or filling up the interstices with gravel, which, if 

 used, should be free of earthy particles. But this ad- 

 dition is hardly necessary, where there is much traffic, 

 as the rough and angular sides of the metal soon lock 

 into each other, and form smooth surface. 



After opening a new road, a weighty roller may be 



