an intimate friend of the geographer Strabo, was praefect of Egypt in the reign of Augustus, and some time after Cornelius Gallus, with whom he has often been confounded, had been invested with the same office. His prefecture of Egypt belongs to thee years B. C. 24 and 25, and these years have become remarkable in history through a bold expedition into Arabia, in which, however, Aelius Gallus completely filed. Gallus undertook the expedition from Egypt by the command of Augustus, partly with a view to explore the country and its inhabitants, and partly to conclude treaties of friendship with the people, or to subdue them if they should oppose the Romans, for it was believed at the time that Arabia was full of all kinds of treasures. When Aelius Gallus set out with his army, he trusted to the guidance of a Roman called Syllaeus, who deceived and misled him. A long account of this interesting expedition through the desert is given by Strabo (xvi. p.780, &c.; comp. xvii. pp. 806, 816, 819; and D. C. 53.29). The burning heat of the sun, the bad water, and the want of every thing necessary to support life, produced a disease among the soldiers which was altogether unknown to the Romans, and destroyed the greater part of the army; so that the Arabs were not only not subdued, but succeeded in driving the Romans even from those parts of the country which they had possessed before. Aelius Gallus spent six months on his march into the country, on account of his treacherous guide, while he effected his retreat in sixty days. It would be extremely interesting to trace this expedition of Aelius Gallus into Arabia, but our knowledge of that country is as yet too scanty to enable us to identify the route as described by Strabo, who derived most of his information about Arabia from his friend Aelius Gallus. (Comp. Strab. ii. p.118 ; Plin. Nat. 7.28; J. AJ 15.9.3 ; Galen, vol. ii, p. 455, ed. Basil.)