There are events in the history of a people, which are remembered with difficulty or displeasure and therefore soon drop from the memory of men. But there are other incidents which pass from father to son through many generations, and the remembrance of them, though altered in many particulars and variously recounted, seems to be undying. Events of this kind are migrations, long warfare or decisive battles, which resulted either in defeat or victory, alliances with cognate or friendly tribes, times of abundance, of famines and epidemics. To be of easy remembrance, there must be something connected with these events which forcibly strikes the imagination and in later times stands out as the principal fact, while minor features of its occurrence disappear or become subject to alterations in the progress of time.