Their fleet was now an imposing one for river warfare. They had eighteen steam gun-boats, carrying from six to eight guns each, four iron-clad vessels, three with casemates, and one, the Bahia, a monitor, with revolving turret, and two 150-pounder Whitworth guns, in all one hundred and twenty-five guns. Two of the steamers and the ironclad Tamandaré were sent up the Parana, to reconnoitre, but soon returned, after getting on shore and being in some jeopardy. There was a work on the right or Paraguayan bank, some distance from the confluence, called Itapirú. In the Allied reports it is designated as a fortress. It was really a dilapidated battery, of about thirty yards internal diameter; and at that time armed with one rifled, 12-pounder field gun. The Parana is here quite deep, except in one place, where there was only twelve feet of water in the northern channel, and here some scows, loaded with stones, had been sunk, which closed that channel. The Paraguayans had, at this point, the steamer Gualeguay, armed with two 12-pounders, and two flat-bottomed boats, with an 8-inch gun mounted in each. On the 22d the Gualeguay towed one of these boats down half a mile below Itapirú, and moored her close in under the right bank. The scow at once opened upon the Brazilian fleet, and, in a short time, had put four eight-inch shot into the Admiral’s ship. Three ironclads were sent up as soon as possible, and approached the scow, keeping up an incessant fire. The Paraguayans made excellent practice, in the meantime, with their eight-inch guns, seldom failing to hit one of their opponents. At last the ironclads approached within about one hundred yards, and the crew of the scow left and took to the woods. The Brazilians then lowered and manned three boats, and sent them to take possession of the scow and her gun. As they reached her, some infantry, numbering about one hundred, who were concealed in the woods, gave the boats a volley, which killed or wounded about half of their crews; the rest made off and returned to their vessels. The ironclads then continued to fire at the abandoned scow, and at last blew up the magazine, and she sunk. The gun was not injured, and was recovered by the Paraguayans.