cut through the high, rocky Pesco Montano to let the road pass by the more direct coastal route. (Some authorities hold that the Romans preferred straight roads because the front axles of their vehicles were rigid.) Trajan’s engineers showed their pride in their work by incising monumental Roman numerals, still visible, to mark the depth of the cut every ten feet from the top down, until the road level was triumphantly reached at CXX. Along the Appia, and the other consular roads radiating from Rome, traces of the ancient stone paving are occasionally preserved. The paving blocks are usually _selce_ (flint), polygonal in shape and closely fitted without mortar. While most Roman roads prove on archaeological examination to consist of paving blocks laid in a trench and packed with earth and _selce_ chips, it will be worthwhile to record the ideal method of laying a pavement--strictly speaking a mosaic pavement--as recommended by the architect Vitruvius, a contemporary of Augustus. The method illustrates the Roman engineer’s infinite capacity for taking pains. After the field engineer (1 in the reconstruction, Fig. 12.1), assisted by the stake man (2), had aligned the road with his _groma_, he ran levels with the _chorobates_ (3) with the roadman’s help (4). A plow (5) was used to loosen earth and mark road margins; then workmen dug marginal trenches (6) to the depth desired for the solid foundations. Laborers (7) shoveled loose earth and carried it away in baskets. The next step was to consolidate the roadbed with a tamper (8). Now the roadbed was ready for its foundation, the _pavimentum_ (9), lime mortar or sand laid to form a level base. Next came the _statumen_, or first course (10), fist-size stones, cemented together with mortar or clay, the thickness varying from ten inches to two feet. Over this was laid the _rudus_ or second course (11), nine to twelve inches of lime concrete, grouted with broken stone and pottery fragments. Next the _nucleus_, or third course (12), concrete made of gravel or coarse sand mixed with hot lime, placed in layers and compacted with a roller. Its thickness was one foot at the sides, eighteen inches at the crown of the road. Finally, the _summum dorsum_ or top course (13), polygonal blocks of _selce_ six inches or more thick, carefully fitted and set in the _nucleus_ while the concrete was still soft. Sometimes, when archaeologists have taken up a stretch of Roman road, they have found the _selce_ blocks rutted on the under side: the economical contractors, happily untroubled by high-priced labor, had repaired their road by turning the worn blocks upside down. Standard curbs (14a and b) were two feet wide and eighteen inches high; paved footpaths (15a and b) often ran outside them. Conduits (16) under the curb, with arched outlets (17) opening beside the right of way, took care of draining surface water. Milestones (18) marked the distance from Rome and the name of the Emperor responsible for repairs.