Page:Report from the Select Committee on Steam Carriages.pdf/217



Mr. John Macneil. 6 September, 1831. {|
 * + and when travelled by Waggons:
 * Atmospheric changes || | 20
 * Waggon wheels || | 33.5
 * Horses' feet that draw them. || | 44.5
 * undefined || | 100
 * }
 * Horses' feet that draw them. || | 44.5
 * undefined || | 100
 * }
 * }

What is the effect of travelling by coaches and horses; whence and in what proportion does the injury or deterioration arise; the crushing of materials; their actual wear; their displacement?—If the wheels of Carriages be properly constructed, and cylindrical, the friction, and consequently the wear, on the surface of a well-made road, will be very little, and there will be no injury from displacement of materials, except what may arise from the few surface-stones that will sometimes be started out by the feet of horses on steep hills, when they are obliged to exert a great force to draw up a heavy load. When stones are thus thrown out on a hard and solid surface, the wheels of heavy Carriages will crush them, and cause an injury which would be much more than that caused by the actual wear of the wheels passing over the surface. If the roads be weak or elastic, and bend or yield under the pressure of the wheels, the particles of which it is composed will move and rub against each other, or perhaps break by the action of heavy wheels over them. On such roads. I conceive the injury caused by Steam Carriages will be much greater in proportion to the injury caused by light Carriages drawn by horses, than it will be on solid firm roads. In one instance, where an accurate experiment was made, the wear was found to be four inches of hard stone, when it was placed on a wet clay bottom, while it was not more than half an inch, on a solid dry foundation, (formed as described in the Report of the Select Committee on the Holyhead Road, on the 30th May 1830,) or with a pavement bottom, on a part of the same road, when it was subject to the same traffic. On the Highgate Archway Road before mentioned, the annual wear does not appear to be more than half