“Margot Gayle, who marshaled shrewdness, gentility and spunk to save the Victorian cast-iron buildings of New York — using a little magnet as a demonstration device — in a crusade that led to the preservation of historic SoHo, died Sunday at her home in Manhattan. … Ms. Gayle’s crowning achievement was helping to win the establishment of the SoHo-Cast Iron Historic District, encompassing 26 blocks in what was originally an industrial quarter known as Hell’s Hundred Acres.”