274 THE DECLINE AND FALL [Chap, xl engineers understood the methods of conducting deep mines, and of raising platforms to the level of the rampart ; he shook the strongest battlements with his military engines, and some- times advanced to the assault with a line of moveable turrets on the backs of elephants. In the great cities of the East, the disadvantage of space, perhaps of position, was compensated by the zeal of the people, who seconded the garrison in the defence of their country and religion ; and the fabulous promise of the Son of God, that Edessa should never be taken, filled the citizens with valiant confidence, and chilled the besiegers with doubt and dismay. 132 The subordinate towns of Armenia and Meso- potamia were diligently strengthened, and the posts which ap- peared to have any command of ground or water were occupied by numerous forts, substantially built of stone, or more hastily erected with the obvious materials of earth and brick. The eye of Justinian investigated every spot ; and his cruel pre- cautions might attract the war into some lonely vale, whose peaceful natives, connected by trade and marriage, were ignor- ant of national discord and the quarrels of princes. Westward of the Euphrates, a sandy desert extends above six hundred miles to the Ked Sea. Nature had interposed a vacant solitude between the ambition of two rival empires; the Arabians, till Mahomet arose, were formidable only as robbers; and, in the proud security of peace, the fortifications of Syria were neglected on the most vulnerable side. Death of But the national enmity, at least the effects of that enmity, king of ' had been suspended by a truce, which continued above four- a.d. 488 score years. An ambassador from the emperor Zeno ac- companied the rash and unfortunate Perozes, in his expedition against the Nepthalites or white Huns, whose conquests had been stretched from the Caspian to the heart of India, whose throne was enriched with emeralds, 133 and whose cavalry 132 Procopius (Persic. 1. ii. c. 12) tells the story with a tone half sceptical, half superstitious, of Herodotus. The promise was not in the primitive lie of Eusebius, but dates at least from the year 400 ; and a third lie, the Veronica, was soon raised on the two former (Evagrius, 1. iv. c. 27). As Edessa has been taken, Tillemont must disclaim the promise (M£m. Eccl^s. torn. i. p. 362, 383, 617). 133 They were purchased from the merchants of Adulis who traded to India (Cosmas, Topograph. Christ. 1. xi. p. 339) ; yet, in the estimate of precious stones, the Scythian emerald was the first, the Bactrian the second, the ^Ethiopian only the third (Hill's Theophrastus, p. 61, &c. 92). The production, mines, &o. of emeralds, are involved in darkness ; and it is doubtful whether we possess any of