CHAMBERS'S INFORMATION FOR THE PEOPLE. 



obstacles either of nature or private property 

 Mountains were perforated, and bold arches 

 thrown over the broadest and most rapid streams 

 The middle part of the road was raised into a 

 terrace which commanded the adjacent country, 

 consisting of several strata of sand, gravel, and 

 cement, and was paved with large stones, or, in 

 some places near the capital, with granite. Such 

 was the solid construction of the Roman high- 

 ways, whose firmness has not entirely yielded to 

 the effect of fifteen centuries. They united the 

 subjects of the most distant provinces by an easy 

 and familiar intercourse ; but their primary object 

 had been to facilitate the marches of the legions : 

 nor was any country considered as completely 

 subdued, till it had been rendered in all its parts 

 pervious to the arms and authority of the con- 

 queror. The advantage of receiving the earliest 

 intelligence, and of conveying their orders with 

 celerity, induced the emperors to establish through- 

 out their extensive dominions the regular institu- 

 tion of posts. Houses were everywhere erected, 

 at the distance of only five or six miles ; each of 

 them was constantly provided with forty horses ; 

 and by the help of these relays, it was easy to 

 travel a hundred miles in a day along the Roman 

 roads. The use of the posts was allowed to those 

 who claimed it by an imperial mandate ; but 

 though originally intended for the public service, 

 it was sometimes indulged to the business or con- 

 veniency of private citizens.' 



From other accounts, we learn that the Roman 

 roads varied in importance and uses. The great 

 lines were called pratorian ways, as being under 

 the direction of the praetors ; and these formed 

 the roads for military intercourse. Other lines 

 were exclusively adapted for commerce or civil 

 intercourse, and were under the direction of 

 consuls. Both kinds were formed in a similar 

 manner. First, all loose and soft matter was 

 removed, and then a solid substructure was laid, 

 consisting of several strata of small stones, broken 

 tiles, and gravel, concreted by cement. Above 

 this was laid the pavement, formed of large hex- 

 agonal blocks of stone, jointed together in the 

 principal roads at least with care. Basaltic lava 

 seems to have been preferred, when it could be 

 had. Various remains of Roman roads of this 

 kind still exist in Italy, France, and also in 

 different parts of Britain. One of the chief 

 Roman thoroughfares, in an oblique direction 

 across the country from London to the west of 

 Scotland, was long known by the name of Wat- 

 ling Street, which has been perpetuated in the 

 appellation of one of the streets in the metro- 

 polis. 



Modern Roads. 



The Roman roads being constructed not for 

 wheeled carriages, but for marching and for beasts 

 of burden, were carried straight from one station 

 to another, without any regard to the level. With 

 modern roads, the case is altogether different. In 

 fact, the skill and ingenuity of the modern road 

 engineer are directed to make the inclinations or 

 gradients, as they are called, easy, with as little 

 expense as possible in excavating and embanking, 

 and to do this without deviating much from the 

 direct course. 



What is the best transverse form for a road, 

 is a much debated question among engineers. All 



438 



agree that it should be higher in the middle than 

 at the sides, but some think it should be much 

 higher than others. As a road can be better kept 

 clear of water by a slight inclination in the direc- 

 tion of its length, than by any form which can be 

 given to its cross section, it seems preferable that 

 it should be as nearly flat as possible, because 

 every part of its breadth will then be equally 

 available for traffic; whereas it is almost neces- 

 sary to keep on the centre of a highly convex 

 road, and consequently wear deep furrows there, 

 by confining the wheels and horses to pretty much 

 the same track. The figure shews a transverse 



' ' ' '* 



Cross Section of a Road : 

 A, Foundation of rough pavement or concrete ; B, Broken stones. 



section of a road of an approved form ; the slope 

 is i in 30, with a few feet in the centre on a flat 

 curve. 



In the construction of the road itself, there are 

 two rival systems, the essential point of difference 

 being whether a hard, firm foundation is necessary 

 or not. Telford considered the foundation of 

 primary importance, and constructed it of rough 

 stones, carefully set on their broad edges, and 

 having the interstices packed by hand with stone 

 chips, thus forming a solid pavement. Macadam, 

 on the contrary, held it to be a matter of indiffer- 

 ence whether the substratum be hard or soft ; he 

 even preferred a yielding and soft foundation to 

 One which was rigid and unyielding, so that even 

 on boggy ground, if it were but firm enough to 

 allow of a man walking over it, he considered an 

 artificial bottoming quite unnecessary. His roads 

 were formed entirely of angular pieces of stone, of 

 such a size as to pass freely through a ring 2^ 

 inches in diameter. This plan has now fewer 

 advocates than Telford's, or than the one subse- 

 quently proposed by Mr Thomas Hughes, where 

 a concrete of gravel and lime is employed for the 

 foundation of the road. But experience has shewn 

 that Macadam's plan of employing angular pieces 

 of stone is superior to every other as a mere 

 covering for roads, whether they have an artificial 

 foundation or not. So popular at one time was 

 the system of macadamising, that expensively 

 paved streets, such as that between Edinburgh 

 and Leith, were torn up to be reformed on the 

 new plan. Dublin has been instanced as an 

 example of the failure of Macadam's plan for the 

 streets of a populous city. There the macadam- 

 ised streets are in winter constantly covered with 

 mud, and in summer, profuse watering is required 

 :o keep them from being overwhelmed with dust, 

 [t is curious, however, that the French road- 

 engineers have, in recent years, come to the con- 

 clusion, that a covering of broken stone alone is 

 sufficient on the most frequented roads and under 

 all but the very heaviest traffic. 



With regard to the kind of stone suitable for 

 covering roads, granite and the different kinds of 

 greenstone and basalt, ordinarily called whin- 

 stones, are the only kinds admissible. Sandstone 

 s too easily crushed, limestone is objectionable 

 rom its slight solubility in water. The stone 



