lloci: II. PAVED ROADS. .1D7 



judges are of opinion with John Farey {Evidence, ^c. 1819.), that a roller cannot be be- 

 neficially used upon a road at any other times but after new coating it with materials, or 

 after a frost, or when the sticking of materials to the wheels may have loosened up the 

 stratum. 



3695. Beatson's new theory of roads, as given in vol. i. of the Communications to the 

 Board of Agriculture, is as follows : Water percolates through porous strata, and is re- 

 tained by compact strata. Whatever may be the form of the surface, therefore, if there 

 is a porous stratum underneath, the surface will be generally dry. When a new road is 

 to be formed, reduce the natural surface so as the lines of a section of it may meet in an 

 angle or ridge in the middle of the road {fig- 550. a), having a slope from thence of 



550 



about an inch in a foot. The road being thus formed, must be allowed to harden and 

 settle for some time, and then covered to a level, by a stratum {b b) sufficiently porous 

 to admit water to pass through it ; small drains (c c) being formed at the sides, to lead 

 the water from the gutters {d d), into the open ditches {e e). Over this is to be laid 

 the coat of hard materials if), which need not be more than 6 or 7 inches in thickness, 

 of stones broken very small, or of the best gravel : it is then to be rolled with a roller, 

 which admits of being loaded, so as to render the surface harder and harder by degrees. 

 The advantages of this construction, Mr. Beatson tells us, are, every part of the road 

 being equally commodious for carriages, and very little repair required. These advan- 

 tages, however, are by no means obvious. 



Sect, IV. Paved Roads. 



3696. Causeways and pavements are chiefly made use of in towns, and may therefore 

 be considered as belonging more to architecture than to agriculture. But as it is the 

 opinion of some of the first engineers, that pavements might be introduced with advantage 

 on the public roads for some distance from the larger towns, we shall shortly consider 

 this subject with reference to that object. Paving, as applied to roads, is therefore to be 

 considered as a substitute for a part or the whole of the metalled part of the road, and 

 not as occupying every part of its width or site, as in the case of streets. 



3697. For roads near capital or great commercial towns, paving, according to Edgeworth, 

 is the only certain method yet known that gives sufficient hardness, smoothness, and 

 permanency. B. and J. Farey are of the same opinion, and the latter considers it 

 would be proper to pave the sides of all the principal entrances into London. W^alkcr, 

 who was the engineer of the Commercial Road, ten feet of the centre of which is paved 

 with granite, and has given great satisfaction for upwards of 1 6 years, is a great advocate 

 for paving. " The advantage," he says, " of paving part of a road where the traffic is 

 great, and the materials for making roads bad or expensive, is not confined to improving 

 the conveyance for heavy goods and reducing the horses' labour ; but as the paving is 

 always preferred for heavy carriages, the sides of a road are left for light carriages, and 

 are kept in much better repair than otherwise they could possibly be. It is not overstating 

 the advantage of the paving, but rather otherwise, to say, that, taking the year through, 

 two horses will do more w^ork, with the same labour to themselves, upon a paved road, than 

 three upon a good gravelled road j if the traffic upon the gravel road is at all considerable, 

 and if the effect of this, in point of expense, is brought into figures, the saving of the 

 expense of carriage will be found to be very great when compared with the cost of the 

 paving. If the annual tonngge upon the Commercial Road is taken at 250,000 tons, and 

 at the rate of only 35. per ton from the docks, it could not upon a gravelled road be done 

 under 45. 6rf., say however 4s., or Is. per ton difference, making a saving of 12,500/., or 

 nearly the whole expense of the paving in one year. The introduction of paving, there- 

 fore, would, in many cases, be productive of great advantage, by improving the gravel 

 road, reducing the expense of repairs, and causing a saving of horses' labour much be- 

 yond what there is any idea of." 



3698. Telford considers that it would be of advantage to pave a part of the centre of 

 great public roads ; and in conformity with this principle, when forming a gravel road, 

 he lays eight or ten feet of it in the centre with stones. 



3699. The parts of the road most desirable to be paved, according to B. Farey, are the 

 sides. " If the centre were paved," he says, " the light carriages would be miicli an- 



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