The milder initial stage of this process is illustrated by the separation of Abram and Lot in the book of Genesis.[192] Abram “was very rich in cattle.” “Lot also had flocks and herds and tents. And the land was not able to bear them that they might dwell together, for their substance was great, so that they could not dwell together. And there was a strife between the herdmen of Abram’s cattle and the herdmen of Lot’s cattle.” They agreed, therefore, to separate, Lot choosing the fertile valley of the Jordan, Abram going to the left into the land of Canaan. Migrations of the same sort, more or less peaceable, are described by modern writers as extending the Russian people from time to time farther and farther to the south and east.[193] In the instances best known to history the migrations were far from peaceable, and the puzzle has been to account for their recurrence. The slaughter of the German barbarians by Marius, Cæsar, Drusus, Tiberius, Germanicus did not prevent the reappearance of similar hordes of invaders a generation later. Claudius destroyed a quarter of a million of Goths; Aurelian and Probus had the same work to do again. Under Diocletian the barbarians, finding the conquest of Rome too much for them, slaughtered one another in frontier wars. No losses seemed to exhaust the permanent possibilities of population in those quarters. At last in the fourth century “clouds of barbarians seemed to collect from all parts of the northern hemisphere. Gathering fresh darkness and terror as they rolled on, the congregated bodies at length obscured the sun of Italy and sunk the Western world in night.”[194]