A historian whose works I have already quoted on several occasions, and who of all men had perhaps with most profit studied human nature, has remarked that the aspiring genius of Rome sacrificed vanity to ambition, deeming it more prudent to adopt virtue and merit for her own wheresoever they were found, among slaves or strangers, enemies or barbarians. This sacrifice it was easy for the Italian race to make; naturally swarthy, and not unfrequently olive-coloured, they met with no race with whom the Romans might not freely amalgamate. Far different is it with modern Europe and her races; follow them to tropical India, Africa, and America, and it will be seen that extinction seems the sure result of all their efforts, whether they unite with the native races or not. If they unite, their purer blood, as we may so call it, soon disappears in the stream of a darker population; if they spurn the union, climate, or as some would term it, malaria, speedily exterminates their race and name. In the first or second chapter of this Essay I ventured to suggest that the discovery of the art to modify the earth, air, and waters of all countries, so as to render them habitable for _all mankind_, was the grand problem man is now called on to solve. In the construction of the continents of the globe, nature seems to have had in view the formation by centres of life of the living inhabitants of the globe. In these centres she placed forms of life equal to sustain their existence, occasionally aided, at other times unaided, by human industry. In the virgin forests of America the aborigines lived and throve; under their hands the earth underwent no modification; to the negro the deadly regions of Central Africa are healthful and pleasant, though at times abandoned to nature, at times deeply modified by human industry. India and Java, the Malayan peninsula, as well as ancient Mexico and China, were many of them highly cultivated regions, in which the aborigines multiplied and enjoyed life; to the European they are premature graves. But when it is attempted to transfer these centres of life to other regions, the attempt has uniformly failed.