A Spiritual is a African-American song with a religious text. Traditionally monophonic and a capella, these songs are antecedents of the blues. They began on Southern slaveplantations as work songs[?], sometimes with hidden messages of rebellion and escape from the slaves' owners.
... des Hässlichen (1853)
Die Poesie and ihre Geschichte (1885)
Studien (1839-47)
Neue Studien (1875-78).
He published also an autobiography entitled Von ...