Human history, like all great movements, was cyclical, and returned to the point of beginning. The idea of indefinite progress in a right line was a chimera of the imagination, with no analogue in nature. The parabola of a comet was perhaps a yet better illustration of the career of humanity. Tending upward and sunward from the aphelion of barbarism, the race attained the perihelion of civilization only to plunge downward once more to its nether goal in the regions of chaos.