it was satisfactorily established, not only that carriages propelled by steam were not more injurious than carriages drawn by horses, but that they were considerably less so. To adapt horse coaches to move with the speed necessary for travelling, and for despatches, the tires of the wheels should be of very limited breadth; and latterly, they are even constructed with a round surface, instead of a flat one, towards the road; the section of the tire by a plane through the axle, and at right angles to the wheel, being a semicircle or elongated semi-ellipse. In either case such a wheel must cut up the best and hardest road. The wheels of steam-carriages on the other hand, are most efficient, when constructed with a broad tire, the tires never being less than four or five inches in breadth; and, according to the plans of some projectors, extending even to six or eight inches. The tires being truly cylindrical and not dished, the wheels act upon the road in the manner of rollers, and, instead of wearing it, rather tend to consolidate and render it smooth and firm. Thus a steam-carriage, compared with a horse carriage, in as far as relates to the wheels only, is much less injurious to the road, if, indeed, it can be said to be injurious at all. But a stronger testimony is furnished in favour of steam-carriages by the fact established before the committee, - that the principal part of the wear of roads proceeds, not from wheels but from horses. Indeed, a very slight consideration might have caused this fact to have been foreseen. If the nature of the action of a wheel 2½ inches broad rolling along the road, be compared with the pounding and digging of the iron-shod feet of horses, the question will be readily understood.
From what has been above stated, the qualities
