5. This stage of culture, in its higher development, combines with the fourth and last--city-building, and city-life, when men of the same race, and conscious of a common origin, but practically strangers to each other, form settlements on a large scale, which, being enclosed in walls, become places of refuge and defence, centres of commerce, industry and government. For, when a community has become very numerous, with wants multiplied by continual improvements and increasing culture, each family can no longer make all the things it needs, and a portion of the population devotes itself to manufacture and arts, occupations best pursued in cities, while the other goes on cultivating the land and raising cattle, the two sets of produces--those of nature and those of the cunning hand and brain--being bartered one for the other, or, when coin is invented, exchanged through that more convenient medium. In the same manner, the task of government having become too manifold and complicated for one man, the former Patriarch, now King, is obliged to surround himself with assistants--either the elders of the race, or persons of his own choice,--and send others to different places, to rule in his name and under his authority. The city in which the King and his immediate ministers and officers reside, naturally becomes the most important one--the Capital of the State. 6. It does not follow by any means that a people, once settled, never stirred from its adopted country. The migratory or wandering instinct never quite died out--our own love of travelling sufficiently proves that--and it was no unfrequent occurrence in very ancient times for large tribes, even portions of nations, to start off again in search of new homes and to found new cities, compelled thereto either by the gradual overcrowding of the old country, or by intestine discords, or by the invasion of new nomadic tribes of a different race who drove the old settlers before them to take possession of their settlements, massacred them if they resisted and reduced those who remained to an irksome subjection. Such invasions, of course, might also be perpetrated with the same results by regular armies, led by kings and generals from some other settled and organized country. The alternative between bondage and emigration must have been frequently offered, and the choice in favor of the latter was helped not a little by the spirit of adventure inborn in man, tempted by so many unexplored regions as there were in those remote ages.