In a recently-published work of much learning and great interest, La Frontière de l'Euphrate de Pompée à la Conquète Arabe (Paris, Fontemoing, 1907), M. Victor Chapot has dealt at some length with the history of the eastern legions. But neither he, nor, so far as I can find, any other writer, has attempted to fix their camps with full regard to chronology, and many points have been left uncertain. Although there is little direct evidence—less than for any other part of the Roman Empire—it may be possible to construct with reasonable probability a more exact military map of the eastern frontier.