In July 1897, Du Bois left Philadelphia and took a professorship in history and economics at the historically black Atlanta University in Georgia.  His first major academic work was his book The Philadelphia Negro (1899), a detailed and comprehensive sociological study of the African-American people of Philadelphia, based on the field work he did in 1896–1897. The work was a breakthrough in scholarship, because it was the first scientific study of African Americans and a major contribution to early scientific sociology in the .   In the study, Du Bois coined the phrase "the submerged tenth" to describe the black underclass. Later in 1903 he popularized the term, the " Talented Tenth ", applied to society's elite class.  Du Bois's terminology reflected his opinion that the elite of a nation, both black and white, was critical to achievements in culture and progress.  Du Bois wrote in this period in a dismissive way of the underclass, describing them as "lazy" or "unreliable", but – in contrast to other scholars – he attributed many of their societal problems to the ravages of slavery.