In the year 18 B.C. Ælius Gallus, a Roman knight, then Governor of Egypt, undertook, by order of Augustus, a campaign into Arabia. Strabo, p. 780, says, “Observing that the Red Sea is extremely narrow, and forms an inconsiderable barrier between the Æthiopians and the Arabs, the Emperor ordered Gallus to ‘explore’ both countries, being determined either to make these nations his friends and allies, or to subdue them. As they had from time immemorial been selling the spices and precious stones of their countries for cash, and never imported goods from foreign parts, they were proverbial for their wealth; and this was the principal inducement for making an attempt to win them as friends, or to subdue them in case of resistance. The Emperor was, moreover, encouraged by the Nabatæans, who were allies of the Romans, and promised to further his views.”