Page:Report from the Select Committee on Steam Carriages.pdf/150



Davies Gilbert Esq. M.P. 17 August, 1831. "With reference to the preservation of roads, wheels should be made wide, and so constructed as to allow of the whole breadth bearing at once; and every portion in contact with the ground should roll on it without the least dragging or slide; but, it is evident from the well-known properties of the cycloid, that the above conditions cannot unite unless the roads are perfectly hard, smooth and flat; and, unless the fellies of the wheels, with their tires, are accurately portions of a cylinder; these forms, therefore, of roads and of wheels are the models towards which they should always approximate.

"Roads were heretofore made with a transverse curvature to throw off water, and in that case it seems evident that the peripheries of the wheels should, in their transverse sections, become tangents to this curve, from whence arose the necessity for dishing wheels, and for bending the axes, which contrivances gave some incidental advantage for turning, for protecting the nave, and by affording room for increased stowage above. But recent experience having proved that the curved form of roads is wholly inadequate for obtaining the end proposed, since the smallest rut intercepts the lateral flow of the water; and, that the barrel shape confines Carriages to the middle of the way, and thereby occasions these very ruts; roads are now laid flat. Carriages drive indifferent over every part, the wear is uniform, and not even the appearance of a longitudinal furrow is to be seen. It may, therefore, confidently be hoped that wheels approaching to the cylindrical form will soon find their way into general use.

"The line of traction is mechanically best disposed when it lies exactly parallel to the direction of motion, and its power is diminished at any inclination of that line in the proportions of the cosine of the angle to radius. When obstacles frequently occur, it had better perhaps receive a small inclination upwards, for the purpose of acting with most advantage when those are to be overcome. But it is probable that different animals exert their