A battery of two 18 pounders was opened on the enemy's fleet on Tuesday morning, whilst another of four 9 pounders play'd on their works and camp on Gwyn's Island. In a short time the whole fleet was forced to tow out of reach of the battery; their fire ceased after a few rounds. Their camp was thrown into confusion, and in the night, before we could procure boats to carry over our men, they removed all their tents except one, their cannon except one, and all their stores, &c. There were three tenders in the haven, which attempted to prevent our passage. ー Their works were still manned as if they meant to dispute their ground, but as soon as our soldiers put off in a few canoes, they retreated precipitately to their ships. The tenders fell into our hands, one they set on fire, but our people boarded it and extinguished the flames. The enemy burnt two small vessels, and the night following a very large ship, supposed to be the Dunmore, for she was very much damaged, having received four 18 pound shot through her sides and a double headed one through her stern which raked her. ー Her mate was killed, a sailor had his arm taken off, and Lord Dunmore had his leg wounded by this shot. The fleet has sailed from the Island, which we are in quiet possession of. From their works and preparation for others, and flocks of cattle left on the Island, it is evident they left it much against their inclination and long before they expected it. We found 150 graves and 12 dead negroes lying in the open air. They have had a dreadful fever amongst them, and the small-pox, I wish our army may not catch the infection. The Roebuck was at the mouth of Rappahanock. The Fowey and Otter did not choose to come to the assistance of the Dunmore which, unfortunately for her, had changed stations with the Otter, and by this means came into the jaws of our battery which was concealed. We did not lose a man.