854 THE DECLINE AND FALL CHAP, bating on the side of Aurelian, he received a real and ' effectual aid from this imaginary reinforcement . Fortifica- But whatever confidence might be placed in ideal Rome. ramparts, the experience of the past, and the dread of the future, induced the Romans to construct fortifica- tions of a grosser and more substantial kind. The seven hills of Rome had been surrounded by the suc- cessors of Romulus, with an ancient wall of more than thirteen miles ". The vast enclosure may seem dispro- portioned to the strength and numbers of the infant state. But it was necessary to secure an ample extent of pasture and arable land, against the frequent and sudden incursions of the tribes of Latium, the perpe- tual enemies of the republic. With the progress of Roman greatness, the city and its inhabitants gradually increased, filled up the vacant space, pierced through the useless walls, covered the field of Mars, and, on every side, followed the public highways in long and beautiful suburbs'. The extent of the new walls, erected by Aurehan, and finished in the reign of Pro- bus, was magnified by popular estimation to near fifty *, but is reduced by accurate measurement to about twenty-one, miles". It was a great but a melancholy labour, since the defence of the capital betrayed the decline of the monarchy. The Romans of a more prosperous age, who trusted to the arms of the legions the safety of the frontier camps *, were very far from en- tertaining a suspicion, that it would ever become neces- «> Vopiscus in Hist. Aug. p. 215, 216. gives a long account of these cere- monies, from the registers of the senate. "■ Plin. Hist. Nat. iii. 5. To confirm our idea, we may observe, that for a long time mount Caelius was a grove of oaks, and mount Viminal was overrun with osiers ; that, in the fourth century, the Aventine was a vacant and solitary retirement ; that till the time of Augustus, the Esquiline was an unwholesome burying- ground; and that the numerous inequalities, remarked by the ancients in the Quirinal, sufficiently prove that it was not covered with buildings. Of the seven hills, the Capitoline and Palatine only, with the adjacent valleys, were the primitive habitation of the Roman people. But this subject would require a dissertation.
- Exspatiantia tecta multas addidere urbes, is the expression of Pliny.
- Hist. August, p. 222. Both Lipsius and Isaac Vossius have eagerly
embraced this measure. " See Nardini, Roma Antica, 1. i. c. 8. ^ Tacit. Hist. iv. 23.
