Page:Popular Science Monthly Volume 53.djvu/270

256 cities of Genoa, Nice, and Marseilles. There it divided: one branch turned north directly through France, passing by many important cities till it reached a point near Boulogne, where, as at Brundisium, boats were always in readiness to carry passengers to Britain; the other branch, starting from Marseilles, traversed the Spanish Peninsula to its remotest part. England had its own roads; beginning near Dover, a leading artery ran to the north almost straight to York, while the others traversed the island from east to west.

The length of the Roman system of roads from the Wall of Antoninus in Britain to Jerusalem was four thousand and eighty miles, and, to the extreme limits of the empire on the Euphrates, about four thousand five hundred miles. From city to city the Roman roads usually went in a straight line, property being condemned and appropriated for the public use without the slightest regard for the feelings or rights of its owners, while natural obstacles were almost ignored. Mountains were tunneled, morasses filled with stones and earth; up one side of a hill and down the other went the road, for, as travel was altogether on foot or on horseback, and wheeled vehicles were not used in the country, a steep grade was no objection. Bold arches of heavy, solid stones were thrown across the smaller streams, while great bridges spanned the rivers. Trajan's bridge over the Danube had twenty-one piers of stone built on piling; each end was fortified by a camp and outworks, and when the structure was destroyed its ruins blocked the river. Many Roman arches over mountain gorges and smaller streams are still in existence. In Wales, the Devil's Bridge near Aberystwyth bears testimony to the solid and lasting character of the work done by Roman engineers; in Spain and Portugal many Roman arches remain to show that honest building could be done in the days of the Cæsars. Here and there in the Alps, in the Pyrenees, in the Tyrol, in the Balkans, the remains of a Roman road lead up to the side of a mountain where a half-closed or entirely blocked tunnel once pierced the giant mass. Here and there in the lowlands of the Danube, in the plains of the Po, on the lower waters of Belgium, the trace of a highway leads into the depths of now impassable quagmires, which, however, were no obstacles to the indefatigable road builders.

They did their work well. When a route had been surveyed and a line of road from eight to twenty feet wide was staked out, the surface of the earth within the inclosed limits was all removed until the clay bed was reached. This was densely packed with rammers: a layer of small stones was placed in position and rammed into the clay with heavy mallets, then another layer of stones and sand with cement; then a layer of sand or gravel with lime mortar; then layer after layer of broken stones cemented into one mass, and above all