In order to get any adequate measure for comparison with the nineteenth century we must take not any preceding century, but the whole preceding epoch of human history. We must take into consideration not only the changes effected in science, in the arts, in the possibilities of human intercourse, and in the extension of our knowledge both of the earth and of the whole visible universe, but the means our century has furnished for future advancement. Our author, who has borne such a distinguished part in the intellectual progress of our century, shows clearly that in means for the discovery of truth, for the extension of our control over Nature, and for the alleviation of the ills that beset mankind, the inheritance of the twentieth century from the nineteenth will be greater than our own inheritance from all the centuries that have gone before. Some may regret that, while only one third of Wallace's book is devoted to the successes of the wonderful century, the author finds the remaining two thirds none too much for the enumeration of some of its most notable failures; but it is natural for one who has borne his own distinguished part in all this marvelous progress to ask where the century has fallen short of the enthusiastic hopes of its leaders, what that it might have done it has failed to do, and what lies ready at the hand of the workers who will begin the new century with this rich inheritance of new thoughts, new methods, and new resources. The more we realize the vast possibilities of human welfare which science has given us the more, he says, must we recognize our total failure to make any adequate use of them. Along with this continuous progress in science, in the arts, and in wealth-production, which has dazzled our imaginations to such an extent that we can hardly admit the possibility of any serious evils having accompanied or been caused by it, there has, he says, been many serious failures--intellectual, social, and moral. Some of our great thinkers, he says, have been so impressed by the terrible nature of these failures that they have doubted whether the final result of the work of the century has any balance of good over evil, of happiness over misery, for mankind at large. Wallace is no pessimist, but one who believes that the first step in retrieving our failures is to perceive clearly where we have failed, for he says there can be no doubt of the magnitude of the evils that have grown up or persisted in the midst of all our triumphs over natural forces and our unprecedented growth in wealth and luxury, and he holds it not the least important part of his work to call attention to some of these failures.