‘That which hath wings shall tell the matter’, says the Preacher. Readers of Antiquity do not need to be reminded of the fresh connotation which aerial photography has given to the text, but never before has its truth been so convincingly driven home as it is by the latest achievement of archaeological aviation. It may be said at once that this account of the Eastern frontier is one of the most important and illuminating contributions ever made to the unwritten history of the Roman Empire. Incidentally, as M. Cumont points out in his lucid and appreciative introduction, its usefulness as a guide for future explorers can hardly be over-estimated. Hundreds of miles of a terra incognita have been thoroughly reconnoitred, so that exponents of the older and less spectacular methods now know exactly where it will profit them to ply the spade and pick. And it is certain that their reward will be rich. Though the sandstorms of the desert may bury, they are in other respects far less destructive than cultivation. In course of time the wonders of Dura-Europos will be repeated or, it may be, eclipsed at other sites. Scholars will then be able to reconstruct with confidence the whole organization of the army of the East, a subject that has hitherto been well-nigh hopelessly obscure. A flood of new light will be thrown on the relations of Rome, first to the Parthians, and then to the Sassanians. At long last we shall learn something of the losing battle which Roman civilization had to fight when it was transplanted to a Semitic countryside, studded here and there with Hellenic towns, —something, that is, of the gradual process by which the legions of the West were slowly but surely transformed into a host of Orientals.