ity of Nisibis, forms, like the Nile, an inundation over
the adjacent country. By the labor of the Persians, the course of the
river was stopped below the town, and the waters were confined on every
side by solid mounds of earth. On this artificial lake, a fleet of armed
vessels filled with soldiers, and with engines which discharged stones
of five hundred pounds weight, advanced in order of battle, and engaged,
almost upon a level, the troops which defended the ramparts. *The
irresistible force of the waters was alternately fatal to the contending
parties, till at length a portion of the walls, unable to sustain the
accumulated pressure, gave way at once, and exposed an ample breach of
one hundred and fifty feet. The Persians were instantly driven to the
assault, and the fate of Nisibis depended on the event of the day. The
heavy-armed cavalry, who led the van of a deep column, were embarrassed
in the mud, and great numbers were drowned in the unseen holes which had
been filled by the rushing waters. The elephants, made furious by their
wounds, increased the disorder, and trampled down thousands of the
Persian archers. The Great King, who, from an exalted throne, beheld the
misfortunes of his arms, sounded, with reluctant indignation, the signal
of the retreat, and suspended for some hours the prosecution of the
attack. But the vigilant citizens improved the opportunity of the night;
and the return of day discovered a new wall of six feet in
height, rising every moment to fill up the interval of the breach.
Notwithstanding the disappointment of his hopes, and the loss of more
than twenty thousand men, Sapor still pressed the reduction of Nisibis,
with an obstinate firmness, which could have yielded only to the
necessity of defending the eastern provinces of Persia against a
formidable invasion of the Massagetae. Alarmed by this intelligence, he
hastily relinquished the siege, and marched with rapid diligence
from the banks of the Tigris to those of the Oxus. The danger and
difficulties of the Scythian war engaged him soon afterwards to
conclude, or at least to observe, a truce with the Roman emperor, which
was equally grateful to both princes; as Constantius himself, after the
death of his two brothers, was involved, by the revolutions of the
West, in a civil contest, which required and seemed to exceed the most
vigorous exertion of his undivided strength.

After the partition of the empire, three years had scarcely ela