Lord Howe held on at the head of the Chesapeake until satisfied that his brother no longer needed him.  On the 14th of September he started down the Bay with the squadron and convoy, sending ahead to the Delaware a small division, to aid the army, if necessary.  The winds holding southerly, ten days were required to get to sea; and outside further delay was caused by very heavy weather.  The Admiral there quitted the convoy and hastened up river.  On the 6th of October he was off Chester, ten miles below Philadelphia.  The navy had already been at work for a week, clearing away obstructions, of which there were two lines; both commanded by batteries on the farther, or Jersey, shore of the Delaware.  The lower battery had been carried by troops; and when Howe arrived, the ships, though meeting lively opposition from the American galleys and fire-rafts, had freed the channel for large vessels to approach the upper obstructions.  These were defended not only by a work at Red Bank on the Jersey shore, but also, on the other side of the stream, by a fort called Fort Mifflin, on Mud Island.[18] As the channel at this point, for a distance of half a mile, was only two hundred yards wide, and troops could not reach the island, the position was very strong, and it detained the British for six weeks.  Fort Mifflin was supported by two floating batteries and a number of galleys.  The latter not only fought, offensively and defensively, but maintained the supplies and ammunition of the garrison.

On the 22d of October, a concerted attack, by the army on the works at Red Bank, and by the Navy on Fort Mifflin, resulted disastrously.  The former was repulsed with considerable loss, the officer commanding being killed.  The squadron, consisting of a 64, three frigates, and a sloop, went into action with Mud Island at the same time; but, the channel having shifted, owing possibly to the obstructions, the sixty-four and the sloop grounded, and could not be floated that day.  On the 23d the Americans concentrated their batteries, galleys, and fire-rafts upon the two; and the larger ship took fire and blew up in the midst of the preparations for lightening her.  The sloop was then set on fire and abandoned.

So long as this obstacle remained, all supplies for the British army in Philadelphia had to be carried by boats to the shore, and transported considerable distances by land.  As direct attacks had proved unavailing, more deliberate measures were adopted.  The army built batteries, and the navy sent ashore guns to mount in them; but the decisive blow to Mud Island was given by a small armed ship, the Vigilant, 20, which was successfully piloted through a channel on the west side of the river, and reached the rear of the work, towing with her a floating battery with three 24-pounders.  This was on the 15th of November.  That night the Americans abandoned Fort Mifflin.  Their loss, Beatson says, amounted to near 400 killed and wounded; that of the British to 43.  If this