ANDREA SHALAL U.S. Treasury Secretary Janet Yellen spoke of the "unspeakable cruelty" and enduring consequences of the trans-Atlantic slave trade but said she was heartened by signs of progress and renewal in both the United States and Africa. Yellen visited the House of Slaves, a fort built in the late 18th century on Goree Island off the coast of Senegal as a transit point for human beings before they were forcibly transported across the Atlantic, as she continued a three-country visit to Africa. "I take from this place the importance of redoubling our commitment to fight for our shared principles and the…