ALLENTOWN, Pa. (AP) - July 19, 2006 - A University of Illinois researcher had discovered a fourth copy of a rare letter Abraham Lincoln had written by to the nation's governors in 1861. The letter John Lupton found Tuesday in the Lehigh County Historical Society's holdings was one Lincoln wrote as part of an unsuccessful ratification process for a constitutional amendment Congress adopted during the term of his predecessor, President James Buchanan, that would have made slavery the law of the land. The president remembered for abolishing slavery had been willing to push the amendment as "kind of a carrot...