The ability of races to flourish in climates other than their own is a question of supreme importance to historians and statesmen, and, it need not be said, to emigrants. But it is only lately that it has been studied scientifically, and the results are still tentative. German ethnologists, of what we may call the _aedicephalous_ school, already referred to, regard it as one of the tragedies of nature that the noble Nordic race, to which they think they belong, dies out when it penetrates southwards. In accordance with this law, the yellow-haired Achaeans decayed in Greece, the Lombards in North Italy, the Vandals in Spain and Africa. After a few generations of life in a warm climate the Aryan stock invariably disappears. We shall show reasons for thinking that this theory is much exaggerated; but there is undoubtedly some truth in it. It has been found to be impossible for white men to colonise India, Burma, tropical America, and West Africa. It has been said that 'there is in India no third generation of pure English blood.' It is notoriously difficult to bring up even one generation of white children in India. The French cannot maintain themselves without race admixture in Martinique and Guadaloupe, nor the Dutch in Java, though it is said that the expectation of life for a European in Java is as good as in his own country. It seems to be also true that the blond race suffers most in a hot climate. In the Philippines it was observed that the fair-haired soldiers in the American army succumbed most readily to disease. In Queensland the Italian colonists are said to stand the heat better than the English, and Mr. Roosevelt, among other items of good advice which he bestowed so liberally on the European nations, advised us to populate the torrid parts of Australia with immigrants from the Latin races. In Natal the English families who are settled in the country are said to be enervated by the climate; and on the high plateaux of the interior our countrymen find it necessary to pay periodical visits to the coast, to be unbraced. The early deaths and not infrequent suicides of Rand magnates may indicate that the air of the Transvaal is too stimulating for a life of high tension and excitement. There are even signs that the same may be true in a minor degree of the United States of America. Both the capitalist and the working man, if they come of English stock, seem to wear out more quickly than at home; and the sterility of marriages among the long settled American families is so pronounced that it can hardly be due entirely to voluntary restriction of parentage. The effects of an unsuitable climate are especially shown in nervous disorders, and are therefore likely to tell most heavily on those who engage in intellectual pursuits, and perhaps on women rather more than on men. The sterilising effects of women's higher education in America are incontrovertible, though this inference is hotly denied in England.