Furnished with such a measuring-rod it becomes easier to attempt to bring into some sort of co-ordination the vast mass of facts which have been accumulated in recent years as to prehistoric, neolithic, and palæolithic man; and the glimpses of light respecting the origin, antiquity, and early history of the human race, which have come in from other sciences such as astronomy, geology, zoology, and philology. To do this exhaustively would be an encyclopædic task which I do not pretend to accomplish, but I am not without hope that the following chapters, connected as they are by the one leading idea of tracing human origins backward to their source, may assist inquiry, and create an interest in this most interesting of all questions, especially among the young who are striving after knowledge, and the millions who, not having the time and opportunity for reading technical works, feel a desire to keep themselves abreast of modern thought and of the advanced culture of the close of the nineteenth century. Before examining these records in detail it is well to begin with the general laws upon which historical evidence is based. History begins with writings. All experience shows that what may be transmitted by memory and word of mouth, consists mainly of hymns and portions of ritual, such as the Vedas of the Hindoos; and to a certain extent of heroic poems and ballads in which the historical element is so overlaid by mythology and poetry, that it is impossible to discriminate between fact and fancy. Thus the legend of Hercules is evidently in the main a solar myth, and his twelve labours are related to the signs of the zodiac, but it is possible that there may have been a real Hercules, the actual or eponymic ancestor of the tribe of Heraclides. So, at a later period, the descent of the Romans from the pious Æneas, and of the Britons from another Trojan hero Brute, are obviously fabulous; and at a still more recent date, our own Arthurian legends are evidently a mediæval romance, though it is possible that there may have been a chief of that name of the Christianized Romano-Britons, who opposed a gallant resistance to the flood of Saxon invasion. But to make real history we require something very different; concurrent and uninterrupted testimony of known historians; absence of impossible and obviously fabulous dates and events; and, above all, contemporary records, written or engraved on tombs, temples, and monuments, or preserved in papyri or clay cylinders.