Two of the guns found among the _débris_ at Ballyneety were still fit for use, and with these, his mortars, and field-train, he continued the bombardment, and by the 17th, he had pushed his lines of circumvallation close to the walls of the city. Nor were the besieged less active or determined in their resistance; every foot of the ground was dearly purchased, and no day went by without a sortie of the most desperate character. One of these, which occurred between the 17th and 20th, was of so novel a character as to demand a passing notice. As William's lines approached close to the walls, the fire from within was so fierce as to compel the soldiers to lie close within their trenches during the night. Those opposite the sally-port, between the bridge and St. John's Gate, were occupied by two regiments: the Blue Dutch and the British, between whom no very friendly feelings existed. The Irish, to whom this was known, taking advantage of the darkness, made a lodgement in one of the traverses, and threw in a stealthy fire on the Dutch. The latter seeing no enemy, and observing the British by the flash of the muskets, believed the fire came from them, and answered it by a deadly volley. This was immediately returned, and the two regiments commenced a murderous fire on each other, while the Irish, as occasion offered, directed a volley at each of them. After several had fallen victims to their own stupidity, the real cause was detected by one of the English generals, and troops were brought up to correct the evil, and chastise the authors of it; but these seeing the place getting too hot for them, rushed from their ambush and reached the city with little loss. The affray between the British and Dutch was not easily reconciled. The confusion of languages baffled, for some time, all attempts at explanation, and hostilities continued until both regiments were placed under arrest, and fresh troops stationed in the trenches. The blunder created great mirth among the Irish soldiers, but the besiegers redoubled their vigilance, and surprise was thenceforth a matter of impossibility. The most serious engagement that occurred after this, took place about the 22d, and was forced by the besieged for the purpose of destroying William's heavy guns before they could be got into position. Issuing out in force, at mid-day, they assailed the enemy's centre with such vigor that they drove it from the trenches; the Prince, who was present, retreated towards his quarters; but falling in his hurry, he had scarcely arisen when a cannonball tore up the very spot on which he had fallen, and after receiving a serious contusion from a fragment of a rock, splintered by the shot, he was carried to Ireton's Tower, nor did he appear again until the final assault. But the sortie ended in the repulse of the besieged, and the guns were rescued and placed in position.