Juan da Rosas, having made himself master of La Plata, and taken possession of Buenos Ayres, closed the Rio de La Plata against all strangers. This was contrary to a treaty with the English and French; and accordingly an English and French squadron was despatched to open up the channel of commerce, the lighter vessels forming an expedition to force the Parana. Rear-Admiral Inglefield was commander-in-chief, with his flag on board the _Vernon_. The French squadron was commanded by Admiral Laine. The command of the English force was given to Captain Charles Hotham, of HM steam-frigate _Gorgon_; and he had under him, _Firebrand_, steam-frigate, Captain J Hope; _Philomel_, surveying brig, Commander BJ Sulivan; _Comus_, eighteen guns, Acting Commander EA Inglefield; _Dolphin_, brigantine, Lieutenant R Levinge; _Fanny_, tender, Lieutenant AC Key. On the 18th, the expedition arrived within three miles of the very strong defences General Rosas had caused to be thrown up on the right bank of the Parana, on Punta Obligada, to oppose their progress. This spot was about thirty miles below the river San Nicholas, and a hundred from the mouth of the river. At daylight the following morning the two captains reconnoitred the position of the enemy, and soon discovered that great military skill had been evinced, both in the ground chosen and the plan of defence pursued. The morning of the 20th broke dark and foggy, but about eight a.m. the weather cleared, and a southerly breeze sprang up. At a quarter to nine, the southern division weighed, and with a light wind stood towards the batteries, followed shortly afterwards by the _San Martin_ and _Comus_. The _Dolphin_ and _Pandour_ had previously anchored on the north shore. Two of the _Dolphin's_ crew--R Rowe, gunner's mate, and W Ross, caulker's mate--though severely wounded, refused to leave their quarters till the day was won. At about ten minutes before ten the batteries commenced the action by opening a heavy fire on the _Philomel_ and the southern division, which Commander Sulivan speedily returned with interest. On this occasion the gallant Lieutenant Doyle, of the _Philomel_, had his arm shot away, and for some time his life was despaired of; but, notwithstanding the agony of his wound, he still showed his interest in the progress of the action. On this the _Dolphin_ weighed, to support the ships in action; but as some of her sails were shot away before she could reach her appointed station, the current drove her astern, and compelled her to anchor. Lieutenant Levinge, however, contrived to place her in a position where her guns did good execution; she, however, was unavoidably exposed all the time to a tremendous shower of shot, shell, grape, and rockets, which came flying over her. During it several of her people were wounded; and Mr G Andrews, clerk in charge, was unhappily killed while assisting the surgeon in his duties to the wounded.