At least 26 enslaved people died on the Tennessee plantation of President Andrew Jackson between 1804 and the end of the Civil War in 1865. Where they were laid to rest is knowledge that had been lost to time. But on Wednesday, the Andrew Jackson Foundation announced a discovery: They believe they have found the slave cemetery at The Hermitage, the home of America’s seventh president.An old agricultural report from the 1930s had given them an idea: It mentioned an area that was not cultivated because it contained tall trees and graves. They also suspected the cemetery would be near the center of the 1,000-acre plantation and on land of low agricultural value. Late last year, with the help of an anonymous donor who was interested in the project, they cleared trees and brought in archaeologist James Greene.Physically walking the property to search for depressions and gravestones yielded a possible …