It remains for us to say a few words regarding the facilities for traveling in those ancient times. The great enterprise displayed by the Romans in undertaking and constructing their road-ways, as well domestic as in foreign countries, is familiar to all of us. There are few who have not seen a long, straight, undeviating road, never turning aside to avoid natural obstacles, but pressing right on to its mark, still denoting by its traditional name the track along which the legions marched to victory. The more perfectly constructed of these ways, after the introduction of paving, were among the most durable monuments of Roman skill in art. The road was first marked out, then the loose earth was excavated down to a solid foundation, on which the lowest course of stones, about six inches in diameter, was laid. On these was placed a mass of rough stones cemented by mortar, forming a kind of rubble work. Then followed a layer of bricks and pottery broken small, and analogous to the burnt earth frequently now employed in our own railways. This coat was also united into a mass by mortar, and upon it was laid the permanent roadway, consisting of large polygons of flinty pavement or basaltic lava, the edges of which were trimmed and fitted with the greatest care. We must certainly yield the palm to the Romans in the art of paving. They combined strength and finish to a degree that may well put our own efforts out of sight. Where the road lay over rocks, the two lower layers were dispensed with as unnecessary; and in carrying it across a swampy country they employed foundations of piles. A raised pathway laid with gravel, mounting blocks for equestrians, and mile-stones to mark the distances, completed the appurtenances of a Roman road. The general direction of road repairs and works was assigned to a class of officers and workmen. Numerous military roads intersected the Roman empire, and this facility of internal communication was a main cause of its duration. It would exceed our limits to give even the names of the principal. In the construction of bridges, especially such as were of a temporary nature, the Romans were very skillful. Carpentry must have been well understood, in order to form such structures as the bridge thrown across the Rhine by Cæsar in the short space of ten days. Many stone bridges, some of them distinguished for elegance, connected the opposite banks of the Tiber; but the triumph of Roman art in this department, is seen in the bridge, partly of stone and partly of wood, built by Trajan across the Danube. The whole length of this structure was 3010 feet. There were twenty-two wooden arches supported on stone piers, each arch having a span of about 130 feet. Coffer-dams were used in constructing the foundations of piers.