with his rams, and sapped them with mines.  But finding that by these means he made no satisfactory progress, he had recourse shortly to wholly novel proceedings.  The river Mygdonius (now the Jerujer), swollen by the melting of the snows in the Mons Masius, had overflowed its banks and covered with an inundation the plain in which Nisibis stands.  Sapor saw that the forces of nature might be employed to advance his ends, and so embanked the lower part of the plain that the water could not run off, but formed a deep lake round the town, gradually creeping up the walls till it had almost reached the battlements.  Having thus created an artificial sea, the energetic monarch rapidly collected, or constructed, a fleet of vessels, and, placing his military engines on board, launched the ships upon the waters, and so attacked the walls of the city at great advantage.  But the defenders resisted stoutly, setting the engines on fire with torches, and either lifting the ships from the water by means of cranes, or else shattering them with the huge stones which they could discharge from their balistics.  Still, therefore, no impression was made; but at last an unforeseen circumstance brought the besieged into the greatest peril, and almost gave Nisibis into the enemy’s hands.  The inundation, confined by the mounds of the Persians, which prevented it from running off, pressed with continually increasing force against the defences of the city, till at last the wall, in one part, proved too weak to withstand the tremendous weight which bore upon it, and gave way suddenly for the space of a hundred and fifty feet.  What further damage was done to the town we know not; but a breach was opened through which the Persians at once made ready to pour into the place, regarding it as impossible that so huge a gap should be either repaired or effectually defended.  Sapor took up his position on an artificial eminence, while his troops rushed to the assault.  First of all marched the heavy cavalry, accompanied by the horse-archers; next came the elephants, bearing iron towers upon their backs, and in each tower a number of bowmen; intermixed with the elephants were a certain amount of heavy-armed foot.  It was a strange column with which to attack a breach; and its composition does not say much for Persian siege tactics, which were always poor and ineffective, and which now, as usually, resulted in failure.  The horses became quickly entangled in the ooze and mud which the waters had left behind them as they subsided; the elephants were even less able to overcome these difficulties, and as soon as they received a wound sank down—­never to rise again—­in the swamp.  Sapor hastily gave orders for the assailing column to retreat and seek the friendly shelter of the Persian camp, while he essayed to maintain his advantage in a different way.  His light archers were ordered to the front, and, being formed into divisions which were to act as reliefs, received orders to prevent the restoration