I should not be disposed to estimate the population of England and Wales, at the retirement of the Romans, at more than 1,500,000. They were like a flock of sheep without masters, and, deprived of the watch-dogs which over-awed and protected them, fell an easy prey to the invaders. III. THE SCANDINAVIANS. The Roman legions and the outlying semi-military settlements along the Rhine and the Danube, forming a cordon reaching from the German Ocean to the Black Sea, kept back the tide of barbarians, but the volume of force accumulated behind the barrier, and at length it poured in an overwhelming and destructive tide over the fair and fertile provinces whose weak and effeminate people offered but a feeble resistance to the robust armies of the north. The Romans, under the instruction of Caesar and Tacitus, had a faint idea of the usages of the people inhabiting the verge that lay around the Roman dominions, but they had no knowledge of the influences that prevailed in "the womb of nations," as Central Europe appeared to the Latins, who saw emerging therefrom hosts of warriors, bearing with them their wives, their children, and their portable effects, determined to win a settlement amid the fertile regions owned and improved by the Romans. These incursions were not colonization in the sense in which Rome understood it; they were the migrations of a people, and were as full, as complete, and as extensive as the Israelitish invasion of Canaan--they were more destructive of property, but less fatal to life. These migratory hosts left a desert behind them, and they either gained a settlement or perished. The Roman colonies preserved their connection with the parent stem, and invoked aid when in need; but the barbarian hosts had no home, no reserves. Other races, moving with similar intent, settled on the land they had vacated. These brought their own social arrangements, and it is very difficult to connect the land system established by the aborigines with the system which, after a lapse of some hundreds of years, was found to prevail in another tribe or nation which had occupied the region that had been vacated.