This then is the great mystery which this little treatise proposes to solve, as well as to show the first steps in the progress of Civilization, the origin and institution of Letters and Literature. On the delicate subject of the integrity of the Races, let it be also understood that we propose, so far as the Pure Races are concerned, to have once and forever settled that they are indestructible, as proven in this treatise. That, as in the substance and science of Chemistry, the two extremes, saccharine and acid, the most intense sweetness and the most intense sourness, are produced by the same material and essential properties, so is it in the substance and science of animal chemistry in the human family in relation to color or complexion of the skin.