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draught presses most on the corresponding shoulder of the horse,which leads the animal to strive to regain the middle, and neces-sarily continues the track to this one part of the road. Thissame inconvenience would result from a concave shape, in pro-portion to the depth of the hollow ; at same time, by throwingall the rain-water falling upon the road into the middle of it, thetrack of the horse’s feet would soon become mire. The exactlevel would, in respect of wetness, be preferable to the concave;and as the weight must ever be equal on both wheels, no trackwould be preferable to another. In an inclined plane, no trackwould be preferable to another; water might get pretty easilyoff; but the weight would always rest unequally on the wheels,causing unequal wear; and in hard frosts, this shape would beextremely dangerous. It must be stated, however, that the con-cave figure (which is unknown in Scotland ) is said to have beenadopted, and to have given satisfaction in some parts of Eng-land, where it is also the practice, occasionally, to clean suchroads, by the admission of a stream of water.
In the original formation of roads, rolling has been recom-mended, for consolidation of the materials ; as also barrowing,followed by rolling, for filling up ruts, in the course of repair.But as a roller cannot press regularly but upon a rectilinear sur-face, if rolling is thought requisite, the road should, in its for-mation, be made of two planes, inclining to the side ditches, andmeeting in the centre of the road, at perhaps an angle of 175°.
Though provision is made for receiving and conveying thewater running from the crown down the sides of the road, andfor keeping off the water coming from contiguous lands, by sideditches and underground conduits, it is yet found, that the rain-water falling upon the road itself, will often run along it, for along space, in the horse-tracks, or ruts made by wheels. Toremedy this, paved surface-gutters, very shallow, have been re-commended to be carried, at short distances, across the road.
In all roads, (except those on a dead level, or a single inclin-ed plane), whether they rise or sink in the middle, the draught-horse cannot move at ease, but when walking in the middle ofthe road; cf course the wear of the road is confined to one track.To counteract this inconvenience, various plans have been sug-gested, either to compel all wheels to be broader in the shoeing,that they may act as rollers, in compressing, instead of cuttingthe road ; or to provide for a varied track, by conypelling everyperson, having more carriages of any sort than one, to haveaxles of different lengths for the wheels of each carriage. Avaried track has been also successfully enforced in the upperward of Clydesdale, from a peculiar mode adopted in repairingthe road, which is to fill up only one of the ruts made by thewheels at one time, v-hich necessarily compels a desertion of theold track, and a more equal distribution of the tear and wear,t i