Author Bernadette Rule will discuss her latest book, The Arithmetic of Color, at the next meeting of the Jackson Purchase Historical Society at 10:30 a.m. Saturday, April 26, at the Graves County Public Library in Mayfield. The meeting is free and open to the public. The Arithmetic of Color is the biography of Tom Johnson, a Graves County man of mixed race who lived from 1871 to 1929. Based on a true story meticulously researched, the book is written as a novel because of its dramatic character. Johnson’s life is at the center of the American experience, including poverty, middle…