Sir Charles Hotham having consulted Captain Hope and Captain Trehouart, who highly approved of the plan, provided the ground when reconnoitred was found as suitable as expected, the execution of it was entrusted to Lieutenant Mackinnon, of the _Alecto_, with Lieutenant Barnard, of the _Firebrand_, as his second. For several days the preparations were going on; and on the 25th of May, all being ready, the convoy and men-of-war dropped down the river, and anchored about five miles above the batteries of San Lorenzo, while the _Alecto_, continuing her course, brought up still nearer to them. At length, on the night of the 1st of June, Sir Charles Hotham and the French captain, with some other officers, reconnoitred the locality. Besides the island we have spoken of, there were several others of nearly the same size, and at the same distance from the western shore; to the eastward of them, again, was an immense archipelago of low swampy islands, covered with brushwood, extending in that direction six or eight miles between them and the main shore of Entre Rios. There was just sufficient light for the reconnoitring party to see their way as they steered through the intricate passages to the east of the large islands. With muffled oars and in dead silence they pulled on till they reached the island they wished to examine; and as they shoved the boat's bow into the mud, a loud rustling was heard in the brushwood, and a wild beast of some sort, which they took for a tiger, rushed towards them. They dared not fire, of course, and without allowing a moment's hesitation to interfere with the service they were upon, proceeded to land according to seniority. As the first officers leaped on shore, sword in hand, the supposed tiger, with a loud snort, jumped into the river, proving to be a harmless capybara, or water-hog, peculiar to the large rivers of South America. They now advanced cautiously, among the reeds and brushwood, across the island, when, to their great satisfaction, they found that the river itself had performed the very work required, by throwing up, when swelled by the rains, an embankment many feet high along the entire length of the island, so as completely to screen them from the enemy's batteries,--a work, indeed, which many hundred men could not so well have executed in a week. Behind this the land rising, there was consequently a large natural trench; here the rockets might be placed in comparative safety. The only difficulty would be to get the men into the trench and to retire safely after the ammunition was expended, and also to avoid any suspicion on the enemy's part of the proximity of such a foe. The party then returned to the ship, and completed the necessary preparations.