HOW THESE ROADS WERE BUILT. In planning their roads the Romans did not hesitate before obstacles like hills or deep valleys or marshy lands. They often pierced the hills with tunnels and bridged the valleys or swamps. In building a road they dug a trench about fifteen feet wide and pounded the earth at the bottom until it was hard. Upon this bottom was placed a layer of rough stones, over which were put nine inches of broken stone mixed with lime to form a sort of concrete. This was covered by a layer six inches deep of broken bricks or broken tiles, which when pounded down offered a hard, smooth surface. On the top were laid large paving stones carefully fitted so that there need be no jar when a wagon rolled over the road. Such roads were necessary for the traders who passed to and fro throughout the empire, but especially for troops or government messengers sent with all speed to regions where there was danger of revolt or where the frontiers were threatened by the barbarians. [Illustration: CROSS-SECTION OF A ROMAN ROAD] AQUEDUCTS. Next to their roads the most remarkable Roman structures were the aqueducts which brought water to the city from rivers or springs, some of them many miles away. Had they known, as we do, how to make heavy iron pipes, their aqueducts would have been laid underground, except where they crossed deep valleys. The lead pipes which they used were not strong enough to endure the force of a great quantity of water, and so when the aqueducts reached the edge of the plain which stretches from the eastern hills to the walls of Rome, the streams of flowing water were carried in stone channels resting upon arches which sometimes reached the height of over ninety feet. THE CLAUDIAN AQUEDUCT. The Claudian aqueduct, which is the most magnificent ever built, is carried on such arches for about seven miles and a half. Although broken in many places, and though the water has not flowed through its lofty channels for sixteen hundred years, it is one of the grandest sights in the neighborhood of Rome. If we add together the lengths of the aqueducts, underground or carried on arches, which provided Rome with her water supply, the total is over three hundred miles. They could furnish Rome with a hundred million gallons of water a day. [Illustration: RUINS OF THE CLAUDIAN AQUEDUCT Completed by the Roman Emperor Claudian in 52 A.D. The structure was nearly a hundred feet high] PUBLIC BATHS. The Romans used great quantities of water for their public baths, which were large buildings with rooms especially made for bathing in hot or cold water and for plunges. They were also, like the Greek gymnasiums, places for exercise, conversation, and reading. Many were built as monuments by wealthy men and by emperors. A very small fee was charged for entrance, and the money was used to pay for repairs and the wages of those who managed the baths.