in such public enterprise, with no return in income or local employment commensurate with the capital involved. So one major conclusion from Ashby’s and Miss Van Deman’s work is that the Romans were better engineers than they were economists. Let the last word on aqueducts be Pliny the Elder’s: “If one takes careful account of the abundant supply of water for public purposes, for baths, pools, channels, houses, gardens, suburban villas; the length of the aqueducts’ courses--arches reared, mountains tunnelled, valleys crossed on the level--he will confess that there has never been a greater marvel in the whole world.” * * * * * One of the latest pieces of Roman engineering, to a knowledge of which archaeology has recently contributed, is Aurelian’s Wall. It has been meticulously studied by a pupil of Ashby’s, I. A. Richmond, now Professor of Archaeology of the Roman Empire at Oxford. Two-thirds of it is still standing (Fig. 12.10), to the disgust of those interested in the unimpeded flow of Rome’s traffic, to the delight of those in love with Rome’s past. It was twelve miles long, twelve feet thick, sixty feet high; it had 381 towers, each with a latrine, and eighteen portcullised gates, nine of which survive (Fig. 12.11). Though the Renaissance humanist Poggio Bracciolini had examined the wall as early as 1431, and the Frenchman Nicholas Audebert had studied it scientifically in 1574, Richmond was still able to make important contributions. He emphasizes, for example, that one-sixth of the wall incorporated buildings: tombs, houses, park walls, aqueducts, cisterns, porticoes, an amphitheater, a fortress. The inference is that the wall had to be built with speed and economy, in the face of the threat of barbarians in north Italy and a depleted treasury. Strategic reasons, of course, dictated the protection of the aqueducts. The use of tombstones as latrine covers shows, says Richmond, that the wall builders “had their religious scruples under excellent control.” It was a sense of urgency and not solicitude for works of art that prompted them, when they built a garden wall at Porta San Lorenzo into the circuit, to leave the statues in their niches and pack them round with clay. [Illustration: FIG. 12.10 Rome, Aurelian’s Wall, from south, near Porta Appia. (H. Kähler, _Rom und seine Welt_, Pl. 252)] [Illustration: _Aurelian’s Wall and Major Monuments_ LEGEND _Roads and Gates_ I Porta Pinciana--Via Salaria II Porta Salaria III Porta and Via Nomentana IV Porta and Via Tiburtina V Porta Praenestina (Maggiore): major aqueduct junction; Via Praenestina VI Porta Asinaria--Via Tusculana VII Porta and Via Latina VIII Porta and Via Appia IX Porta and Via Ostiensis X Porta and Via Portuensis XI Porta Aureliana (S. Pancrazio); Aquae Alsietina and Traiana; Via Aurelia XII Porta and Via Flaminia