Such considerations as these, the force of which is most strongly felt by those best acquainted with the methods of investigation employed by geologists and archæologists, are forcing us to conclude: (1) That there are indicated in the latest geological formations two distinct human periods, an earlier and a later, characterised by differences of faunæ and of physical conditions, as well as by distinct races of men. (2) That these two periods are separated by a somewhat rapid physical change of the nature of submergence, or by a series of changes locally sudden and generally not long-continued. (3) That it is not improbable that this greatest of all revolutions in human affairs may be the same that has so impressed itself on the memory of the survivors as to form the basis of all the traditions and historical accounts of the Deluge. This being the state of the case, it becomes expedient to review our ideas of the ancient Hebrew records, from which our early, and perhaps crude, impressions of this event were derived, and to ascertain how much of our notions of the Deluge of Genesis may be fairly deduced from the record itself, and how much may be due to more or less correct interpretations, or to our own fancy. In connection with this we may also be able to obtain some guidance as to the value to be attached to the Hebrew document as a veritable and primitive record of the great catastrophe. The key to the understanding of the early human history of Genesis lies in the story of the fall of man, and its sequel in the murder of Abel by his brother Cain, the beginning of that reign of violence which endures even to this day. From this arose the first division of the human race into hostile clans or tribes, the races of Cain and Seth, on which hinges the history, characteristics and fate of antediluvian man; and, as we shall see in the sequel, from this arose profound differences in religious beliefs, which have tinged the theology and superstitions of all subsequent times. Of course, in making this statement I refer to the history given in Genesis, without special reference to its intrinsic truth or credibility, but merely in relation to its interpretation in harmony with its own statements.