The geography of Asia and of Africa necessitated a nomadic life. But the nomads were the terror of all those whom the soil or the advantages of a market had induced to build towns. Agriculture therefore was a religious injunction, because of the perils of the state from nomadism. And in these late and civil countries of England and America these propensities still fight out the old battle, in the nation and in the individual. The nomads of Africa were constrained to wander, by the attacks of the gad-fly, which drives the cattle mad, and so compels the tribe to emigrate in the rainy season and to drive off the cattle to the higher sandy regions. The nomads of Asia follow the pasturage from month to month. In America and Europe the nomadism is of trade and curiosity; a progress, certainly, from the gad-fly of Astaboras to the Anglo and Italo-mania of Boston Bay.