In the cycle of studies which are immediately concerned with the career of mankind, the rate of progress has been no less marvellous. The scientific study of human speech may be said to date from the flash of insight which led Friedrich Schlegel in 1808 to detect the kinship between the Aryan languages. From this beginning to the researches of Fick and Ascoli in our own time, the quantity of achievement rivals anything the physical sciences can show. The study of comparative mythology, which has thrown such light upon the primitive thoughts of mankind, is still younger,--is still, indeed, in its infancy. The application of the comparative method to the investigation of laws and customs, of political and ecclesiastical and industrial systems, has been carried on scarcely thirty years; yet the results already obtained are obliging us to rewrite the history of mankind in all its stages. The great achievements of archæologists--the decipherment of Egyptian hieroglyphs and of cuneiform inscriptions in Assyria and Persia, the unearthing of ancient cities, the discovery and classification of primeval implements and works of art in all quarters of the globe--belong almost entirely to the nineteenth century. These discoveries, which have well-nigh doubled for us the length of the historic period, have united with the quite modern revelations of geology concerning the ancient glaciation of the temperate zones, to give us an approximate idea of the age of the human race[1] and the circumstances attending its diffusion over the earth. It has thus at length become possible to obtain something like the outlines of a comprehensive view of the history of the creation, from the earliest stages of condensation of our solar nebula down to the very time in which we live, and to infer from the characteristics of this past evolution some of the most general tendencies of the future.