Marking the bicentenary of the abolishment of the transatlantic slave trade, British historian Simon Schama spoke to a full house on the different responses in America and Britain to this historic event. Schama recently authored “Rough Crossings: Britain, the Slaves, and the American Revolution,” which won the 2006 National Book Critics’ Circle Award for general nonfiction. His thirty-plus films for the BBC include the Emmy-nominated “A History of Britain” and the eight-part “Power of Art. ” Schama also writes regularly for “The Guardian” and “The New Yorker” and won a National Magazine Award for his art criticism in 1996.