When history is conceived as dynamic, as moving, its economic and industrial aspects are emphasized. These are but technical terms which express the problem with which humanity is unceasingly engaged; how to live, how to master and use nature so as to make it tributary to the enrichment of human life. The great advances in civilization have come through those manifestations of intelligence which have lifted man from his precarious subjection to nature, and revealed to him how he may make its forces co-operate with his own purposes. The social world in which the child now lives is so rich and full that it is not easy to see how much it cost, how much effort and thought lie back of it. Man has a tremendous equipment ready at hand. The child may be led to translate these ready-made resources into fluid terms; he may be led to see man face to face with nature, without inherited capital, without tools, without manufactured materials. And, step by step, he may follow the processes by which man recognized the needs of his situation, thought out the weapons and instruments that enable him to cope with them; and may learn how these new resources opened new horizons of growth and created new problems. The industrial history of man is not a materialistic or merely utilitarian affair. It is a matter of intelligence. Its record is the record of how man learned to think, to think to some effect, to transform the conditions of life so that life itself became a different thing. It is an ethical record as well; the account of the conditions which men have patiently wrought out to serve their ends. The question of how human beings live, indeed, represents the dominant interest with which the child approaches historic material. It is this point of view which brings those who worked in the past close to the beings with whom he is daily associated, and confers upon him the gift of sympathetic penetration. The child who is interested in the way in which men lived, the tools they had to do with, the new inventions they made, the transformations of life that arose from the power and leisure thus gained, is eager to repeat like processes in his own action, to remake utensils, to reproduce processes, to rehandle materials. Since he understands their problems and their successes only by seeing what obstacles and what resources they had from nature, the child is interested in field and forest, ocean and mountain, plant and animal. By building up a conception of the natural environment in which lived the people he is studying, he gets his hold upon their lives. This reproduction he cannot make excepting as he gains acquaintance with the natural forces and forms with which he is himself surrounded. The interest in history gives a more human coloring, a wider significance, to his own study of nature. His knowledge of nature lends point and accuracy to his study of history. This is the natural “correlation” of history and science.