The production of the largest numbers of eminent men by peoples of mixed and blended racial elements, not too widely different, is what biological knowledge would lead us to expect. For, if a subrace is produced by crossing of varieties, it will be one of much greater variability than a pure race; as we see in the cases of the domesticated horse and dog and pigeon, of which the modern varieties are only kept pure by continual rejection of the departures from the standards, and of which the great variability renders possible the production, by selection of very marked new features in a brief period of time. The many elements which go to form the mental constitution of an individual become, in a mixed race, variously combined. If the crossed races are very widely different, the results seem to be in nearly all cases bad. The character of the cross-bred is made up of divergent inharmonious tendencies, which give rise to internal conflict, just as the physical features appear in bizarre combination; what examples we have—the Spanish Americans, the Eurasians, the Mulattoes, the half-breeds of Java and Canada—seem to show that a people so composed will produce few great men and will not become a great nation. But, when the crossed races are less widely divergent, the elements of which the mental constitution is composed (and which direct observation and analogy with physical heredity show to be transmitted more or less independently of one another from parent to offspring) have opportunities to come together in new combinations, which result in mental constitutions unlike those of either parent (that is to say, the cross-breds are variable); and among these new combinations, while some will form minds below the average, others will form minds above the average in various degrees; and these, so long as the constitution is not too much weakened by radical lack of harmony of its elements, will be the effective great men. Incidentally, these considerations perhaps throw light on a fact much discussed—namely, that exceptional powers, especially when of highly specialised nature, are often exhibited by persons of unstable mental constitution; whence arises the popular belief that genius is allied to, or is a form of, insanity.