For the first time since a pre-Revolutionary stone wall was discovered in Lower Manhattan last fall, part of it went on display to the public today in Battery Park. An exhibition about the discovery, titled "Walls Within Walls," was unveiled Tuesday evening before a dinner for the Battery Conservancy, which raises money to maintain and improve the 23-acre park. The display, at the Castle Clinton monument, includes just a piece of the first of three large sections of wall that were found during excavation for a new South Ferry subway station. Some archaeologists who have studied parts of the wall...