This recent and important action between iron-clad vessels, at sea, is remarkable in many ways, and is especially interesting to naval men, as armored vessels had, with perhaps a single exception, not come together before, upon the high seas. Fortunately, we have accounts of the battle from Lieutenants Mason and Ingersoll, of the United States Navy, Clements Markham, Lieutenant Madan, R. N., and others--of whose accounts this article will be a condensation. The action took place in the forenoon, off Mexillones de Bolivia. The “Huascar,” a Peruvian man-of-war, was of the old type of English turret ships, and had been employed continuously, at sea, for many months, so that her bottom was very foul, while her boilers were not in condition to make steam properly. These two causes had very much reduced her speed. Her commander, Admiral Grau, had wished to overhaul her, but his representations were overruled, from considerations of policy, and she was despatched to the south, upon what proved to be her last cruise under the Peruvian flag. When in order, she was known to be much faster than the Chilian vessels which she was to encounter, and her loss may fairly be put down to this disregard of professional advice and warning. The Chilian ironclad, “Almirante Cochrane,” her principal opponent, as well as the “Blanco Encalada,” which participated in the latter part of the action, were nearly new casemated vessels; and their constructor, Mr. Reed, had said that they ought to sink the “Huascar” in five minutes. This latter vessel had done good service in the war between Peru and Chili, in interfering with the only transportation possible for the Chilians, who were the aggressors, and who carried the war into the Peruvian boundaries. Her commander, Rear-Admiral Grau, was an excellent officer, and rendered himself quite famous by his sudden dashes into Chilian ports, capturing transports and lighters, and interfering with the submarine cable, so necessary for the success of the Chilian operations. The “Huascar” had made four successful cruises, or rather “raids,” to the southward, in one of which she had captured the “Rimac,” a fine steamer, having on board a fully-equipped battalion of cavalry and a large amount of military stores. Among other curious things which came under the latter head was a complete outfit of water-skins, which were being sent to the Chilian Army at Antofagasta, to enable it to carry water, in crossing the desert of Atacama, to operate upon the province of Tarapaca. This desert had been discovered to contain an immense deposit of nitrate of soda, and the struggle which had been impending for some years between the two nations was precipitated by the desire of Chili to possess this source of wealth.