Page:Remarks on the Present System of Road Making (1823).djvu/197

 *veller; the materials of the road then form a more solid compact mass than when they are laid in thin strata, at different times, for the same reason that a deep arch of uniform materials is preferable to a number of separate rings. Though I state that an inclination in the longitudinal section of the road is always desirable for the purpose of clearing it of water, I am not of the opinion of those who recommend the road to be made and kept flat or level in its gross section. The variety of opinions and practice upon this point are very great; both extremes appear to me to be bad. A road much rounded is dangerous, particularly if the cross section approaches towards the segment of a circle, the slope in the case not being uniform, but increasing rapidly from the nature of the curve, as we depart from the middle or vertical line. The over rounding of roads is also injurious to them, by either confining the heavy carriages to one track in the crown of the road, or if they go upon the sides, by the great wear they produce, from their constant tendency to move down the inclined plane, owing to the angle which the surface of the road and the line of gravity of the load form with each other, and as this tendency is perpendicular to the line of draught, the labour of the horse and the wear of the carriage wheels, are both much increased by it.

It is not altogether foreign to the subject to notice here, the error of forming the inclination of the road-way upon bridges, in the direction of their length, or across the river, from a section of a curve for the whole length, rather than from two lines joined together by a curve, as I have recommended for the cross section of a road. It is to this cause that the very heavy pull is owing, which must have been noticed in just getting upon a bridge, which decreases as we advance towards the middle of the bridge, and which