Ta-daaa! This opening in the floor was the protected position from which Lay Torpedoes would enter the river, notionally smiting any enemy vessels that had managed to make it this far up the Delaware. Actually this was really a test facility more than anything else, though testing something as ridiculously unstable and destructive as a torpedo steered by electric impulses in 1875 on such a busy river seems foolhardy at best. These torpedoes were also tested in the Narragansett Bay at Newport, Rhode Island (watched o'er by Fort Adams), where there's plenty of room for a torpedo to go haywire.

Somewhat hilariously, the only time one of John Louis Lay (1833-1899)'s groundbreaking torpedoes was used in battle was during the Guerra del Pacífico (1879-1883), fought betwixt Peru, Bolivia and Chile. The Peruvian ironclad Huáscar fired a Lay Torpedo in anger, only to have it mysteriously reverse course, heading straight back to where it started. The Huáscar was saved when one of its officers leapt overboard and somehow managed to physically divert the crazed torpedo.