Like exposed photographic paper in a chemical bath, Undertow, 1990, an installation by Simone Mangos, dissolves, blurs, and eventually clarifies into an image of memorable density. Seven large, grainy, black and white photographs of a Berlin cemetery are suspended like scrolls from a ceiling approximately three feet away from the wall. Opposite, six stone windowsills, bricked-in since the gallery’s conversion from a schoolroom, have been excavated. On an accompanying document, a six-panel photograph shows the wire-mesh screen across a canal formerly dividing East from West Berlin. The undertow