Camp 13 Miles from Philadelphia, October 29th, 1777.
[Extract]
SIR,
...Early in the morning of the 23d, six of the enemy's ships warped through the lower row of Chevaux de frise opposite to Billings's Port, which was at first intended to have been defended by batteries, but afterwards rejected through the plan of defence, as being too extensive. The enemy had been some days busied in removing part of the Chiveaux-de-frize from this tier, in doing which, as it was not defended, they found no other difficulty than the labour. After they had all warped through, they made for the upper ties [tier], distant about two and half miles, defended by the batteries on Mud-Island, called Fort Mifflin, and the gallies. When they came within proper distance, they commenced a very furious engagement from three of their nearest ships (the river not being broad enough for more to fight) with the gallies and fort. The cannonade was prodigious, and lasted without intermission six hours, at which time the ships being much disabled, retreated; but the tide being considerably ebbed, and being embarrassed with the fire vessels the gallies carried upon them, two ran aground and were set on fire by the crews, who deserted them, and soon after blew up, with horrid explosions, which were heard an hundred miles in the country. One was the Augusta, of 64 guns; the other a frigate,1 whose name we have not heard. The remaining ship2 that was in the engagement, was more fortunate, she being exceedingly shattered, was towed through the lower Cheveaux de frize. The three ships not in the engagement retired without damage.
These events, considerable in themselves, will have still more considerable consequences.
Philadelphia being situated between two unfordable rivers, is a dangerous post for an enemy to occupy, without having the entire command of the rivers or the country. The American army prevents a communication with the latter, and the gallies and [bateries] by the Delaware. The enemy have now to row their supplies from their shipping at Chester, 15 miles distant, by a communication over Schuylkill, which renders the convoys dangerous, and liable to be [lost] upon the least intelligence being given. Hitherto they have brought them in the night only, but even then they narrowly escape.
This is the situation of the enemy at Philadelphia: they must either get possession of the river, at every risque, and open a communication by water, evacuate the city, or submit to more inconveniences in a blockade, while we can keep the field, then at Boston....
