One must heartily thank the author for the abundant demonstration which follows, well warranting our feeling that these explanations do not suffice--nor yet, in the case of Rome, diminution of population, nor the “brutalities of the gladiatorial shows,” nor “the gratuitous distribution of bread to the urban mobs,” nor yet slavery, lately declared, by Mr. W. R. Paterson, in his _Nemesis of Nations_, to be _the_ cause of the fall of empires. As Mr. Balfour says, “Who can believe that this immemorial custom could, in its decline, destroy the civilisation which, in its vigour, it had helped to create?” It would have been more important, perhaps, to consider, as Mr. Balfour does not, the latest view, advanced by Professor Ronald Ross, that the incursion of malaria may have had something to do with the fall of Rome. =Mr. Balfour's theory--decadence the cause of decadence.=--Mr. Balfour then falls back upon “decadence "as the explanation, and to the critic of this elegant hypothesis that decadence is due to decadence, replies that it is something to recognise the possibility of "subtle changes in the social tissues of old communities.” One regrets all the more that he should not have considered anti-eugenic practices as possibly accounting for these subtle changes. One must, however, quote the excellent passage in which Mr. Balfour supports his use of the word decadence, though one utterly disagrees with the suggestion that the term “old age” might be its equivalent. He says: “The facile generalisations with which we so often season the study of dry historic fact; the habits of political discussion which induce us to catalogue for purposes of debate the outward signs that distinguish (as we are prone to think) the standing from the falling state, hide the obscurer, but more potent, forces which silently prepare the fate of empires.” We may note with interest (and surely with surprise when we consider Japan and Spain and the China of to-morrow), Mr. Balfour's rejection of the doctrine that “arrested progress, and even decadence, may be but the prelude to a new period of vigorous growth. So that even those races or nations which seem frozen into eternal immobility may base upon experience their hopes of an awakening spring.” It is, I fancy, Mr. Balfour's fondness for the Platonic idea of senility in the race as in the individual, that leads him to question what can surely be no longer denied. Thus a little later we find him saying, “_If civilisations wear out, and races become effete_, why should we expect to progress indefinitely, why for us alone is the doom of man to be reversed?”