To the statesman, the student of history, and the general reader, it is hoped that this volume will not be altogether useless, and may assist to a better understanding of many of the problems that have so long puzzled the philosopher. The greatest revolutions in national relations have been accomplished by the migrations of races, the most calamitous wars that have desolated the globe have been the result of the hostility of races. Even now, a cloud is lowering in the horizon. The friend of peace and order watches it with silent anxiety, lest he hasten its coming. The spirit of mischief exults in its approach, but fears to betray his plans. Thus, western and central Europe now present the spectacle of a lull before the storm. Monarchs sit trembling on their thrones, while nations mutter curses. Nor have premonitory symptoms been wanting. Three times, within little more than half a century, have the eruptions of that ever-burning political volcano--France--shaken the social and political system of the civilized world, and shown the amount of combustible materials, which all the efforts of a ruling class cannot always protect from ignition. The grand catastrophe may come within our times. And, is it the result of any particular social condition, the action of any particular class in the social scale, the diffusion of any particular political principles? No, because the revolutionary tendencies are various, and even opposite; if republican in one place, monarchical in another; if democratic in France, aristocratic in Poland. Nor is it a particular social class wherein the revolutionary principle flourishes, for the classes which, in one country, wish subversion, in another, are firmly attached to the established order of things. The poor in Germany are proletarians and revolutionists; in Spain, Portugal, and Italy, the enthusiastic lovers of their king. The better classes in the former country are mostly conservative; in the latter, they are the makers, or rather attempters, of revolutions. Nor is it any particular social condition, for no class is so degraded as it has been; never was poverty less, and prosperity greater in Europe than in the present century; and everywhere the political institutions are more liberal than ever before. Whence, then, this gathering storm? Does it exist only in the minds of the visionary, or is it a mere bugbear of the timorous? Ask the prudent statesman, the traveller who pierces the different strata of the population; look behind the grates of the State-prisons; count--if this be possible--the number of victims of military executions in Germany and Austria, in 1848 and 1849; read the fearful accounts of the taking of Vienna, of Rome, of Ancona, of Venice, during the same short space of time. Everywhere the same cry: Nationality. It is not the temporary ravings of a mob rendered frantic by hunger and misery. It is a question of nationality, a war of races. Happy we who are removed from