I 444. THE DECLINE AND FALL CHAP. There is no difficulty in conceiving the intention of ' the Roman princes to improve their revenue by some restraints upon commerce ; but as Nisibis v^'as situated within their own dominions, and as they were masters both of the imports and exports, it should seem that such restraints were the objects of an internal law, rather than of a foreign treaty. To render them more effectual, some stipulations were probably required on the side of the king of Persia, which appeared so very repugnant either to his interest or to his dignity, that Narses could not be persuaded to subscribe them. As this was the only article to which he refused his con- sent, it was no longer insisted on ; and the emperors either suffered the trade to flow in its natural channels, or contented themselves with such restrictions as it de- pended on their own authority to establish. and articles As soon as this difficulty was removed, a solemn e rea y. ^^^^^ ^^g concluded and ratified between the two nations. The conditions of a treaty so glorious to the empire, and so necessary to Persia, may deserve a more peculiar attention, as the history of Rome presents very few transactions of a similar nature ; most of her wars having either been terminated by absolute conquest, or waged against barbarians ignorant of the use of letters. TheAboras L The Aboras, or, as it is called by Xenophon, the limit be-* ^ Araxes, was fixed as the boundary between the two tween the monarchies ^. That river, which rose near the Tigris, was increased a few miles below Nisibis by the little stream of the Mygdonius, passed under the walls of Singara, and fell into the Euphrates at Circesium, a frontier town, which, by the care of Diocletian, was very strongly fortified Mesopotamia, the object of so many wars, was ceded to the empire ; and the Per- sians, by this treaty, renounced all pretensions to that ^ By an error of the geographer Ptolemy, the position of Singara is removed from the Aboras to the Tigris, which may have produced the mis- take of Peter, in assigning the latter river for the boundary, instead of the former. The line of the Roman frontier traversed, but never followed the course of the Tigris.
- Procopius de Edificiis, 1. ii. c. 6.
