IF the volume now presented to the public were a mere work of art, the history of its misfortune might be written in two very simple words — Too late. The nature and character of slavery have been subjects of an almost endless variety of artistic representation; and after the brilliant achievements in that field, and while those achievements are yet fresh in the memory of the million, he who would add another to the legion, must possess the charm of transcendent exellence, or apologize for something worse than rashness. The reader is, therefore, assured, with all due promptitude, that his attention is not invited to a work of art, but to a work of facts — Facts, terrible and almost ih credible, it may be — yet facts, nevertheless.