It scarcely need be said that the great historical example of conquest is Rome. Her policy was to extend her dominion by making outlying tribes realize that it was to their advantage to acknowledge her sway and pay tribute. So long as they did this quietly and regularly, little else was required of them. As far as possible, the native governmental organization was continued, and simply grafted on to the great Roman stock, the native officials being made subordinates in the Roman organization. Roman traders came and went, carrying culture and civilization with them, and exerting a powerful influence on the mores of the provinces, but the permanent movement of people from the central state was comparatively slight. Alexander the Great was a spreader of conquest, though his early death destroyed whatever possibility there may have been of his establishing a permanent empire. The career of the British government in India has many of the characteristics of conquest. Native rajahs are, to a great extent, utilized as officials of the British government, and there is no large migration of people from England to India, save those connected in some way with the government service, or persons engaged in commercial pursuits, who maintain their permanent home in England. But the influence on the mores of the native inhabitants is great. The third form of migratory movement, which has a particularly close connection with immigration, is colonization. This occurs when a well-established, progressive, and physically vigorous state sends out bodies of citizens, officially as a rule, to settle in certain specified localities. The regions chosen are newly discovered or thinly settled countries, where the native inhabitants are so few, or are on such an inferior stage of culture that they offer but slight resistance to the entrance of the colonists. For while the two previous forms of migration have been warlike, colonization is essentially a peaceful movement. The rivalry for certain favored localities may involve the colonizing power in war with other civilized nations who desire the same thing, but as far as the seizure of the colony itself is concerned, it requires slight military exertion. Colonization, like conquest, is a state enterprise, conducted for the benefit of the state, but differs from it in that its motive is rather the commercial advancement of the state than its military or political aggrandizement. Colonization has often been resorted to, also, when a state has believed itself to be overpopulated, and has aimed directly at improving the condition of its citizens, both those who go and those who are left,—something that is scarcely dreamed of under conquest. Several classifications of colonies have been made. The most satisfactory is that adopted by Professor A. G. Keller, which makes a twofold division into farm and plantation colonies.[9] These differ from each other so much in their essential characteristics that