The test of a book is the service it can render. The character of the service demanded by it is determined by the needs of those to whom it is devoted. This book was not written for the child of five or six years, although children of that age have shown an interest in it. The child of five or six is absorbed in the activities of his own home and his immediate environment. His own neighborhood may well constitute the chief source from which to draw the subject-matter in these early years. Even though many of the processes that he observes are complex, it matters little to the child at this time; for so easily do they lend themselves to dramatic play that they cause him little difficulty. The child at this time, therefore, has no need of this book. But there comes a time when the ideal and the real world begin to separate. No longer content with a "make-believe" process, and unable to control the complex processes of modern life, he feels a need that cannot be satisfied by the resources of his neighborhood alone. There is need of looking elsewhere in order to find experiences that are sufficiently related to his spontaneous activities to enlist his attention, and sufficiently related to what is best in the society in which he lives to form legitimate subject-matter for this period of development. The materials which constitute the subject-matter of this book have been selected and arranged with reference to the needs of the child at such a time. It is the child of six and a half or seven years for whom this book is intended. Were it not true that so many books that are written for children have little regard for real facts, it would seem unnecessary to state that in no case has material been introduced into this book which cannot be justified by reference to a recognized authority in anthropology, paleontology, or geology. The story-form by means of which these facts are conveyed is merely a literary device for bringing home to the child the truth that has thus far been ascertained regarding the fundamental steps in the development of our industrial and social institutions.