RUDOLF WITTKOWER (1901-1971) was a German-American art historian. He was on the staff of the Warburg Institute, London, and became professor at the University of London. He then headed the Department of Fine Arts and Archaeology at Columbia. His highly original works in English include "Architectural Principles in the Age of Humanism," "Art and Architecture in Italy, 1600--1750," "Essays in the History of Architecture," "Essays in the History of Art," and "Baroque Art: The Jesuit Contribution." MARGOT WITTKOWER (1902-1995) was born in Berlin and established herself as an interior designer....