We know that our globe has passed through several geological and palæontological epochs; that living beings have not appeared simultaneously, and that the present fauna and flora have been preceded by very different ones. It is natural to ask the question, when man began to inhabit the earth, and to endeavour to determine the moment of the appearance of this being, so similar to other beings in many respects, so exceptional in his most noble faculties, and superior to everything around him. This question of time should be stated precisely; we must understand the sense which may be attributed to it. Let us observe, in the first place, that here we can have no dates properly so called. They only exist in history. Now primitive mankind can have no history in the scientific sense of the word. Most great religions have endeavoured to fill up this gap. But my readers are already aware that I have refused all considerations drawn from such a source, and that I intend to bring forward here none but the results of experiment and observation. I shall then try how far back we can go with the aid of these guides alone, quoting in the first place a few historic dates as terms of comparison. II. The Greeks and Romans, with whom classical education too often terminates, do not take us very far. The former had much more ancient records than the latter, and yet the era of the Olympiads only brings us to the year 776 before our era; according to Hecateus of Miletus, it was in the ninth or tenth century before our era that the gods ceased to intermarry with mortals, and the Trojan war is regarded approximately as having taken place in the eleventh or twelfth century. Beyond this period, it is evident that we are led by Greece into mere mythology, or rather into those legendary times where truth and fable are confounded. The Aryan traditions go further. M. Vivien de Saint Martin, summing up the works of which he is so good a judge, refers the arrival of the Hindoos on the river of Cabul to about the sixteenth or eighteenth century before our era. These tribes were only an offshoot of the great emigration which the Zend-Avesta takes back almost as far as the Bolor. We can, therefore, refer the latter to the twentieth or twenty-eighth century before our era. Jewish history, starting with Abraham, goes back almost to the same period (2296 years); the deluge of Noah, according to the estimation generally received, to the year 3308. Say about thirty centuries. In China, the Chou-King places the reign of Hoang-ti in the year 2698, and that of Jao in the year 2357 before our era. This would correspond almost to a century, with the date of the migration of Abraham.