In offering the American public a carefully studied outline of its national park system, I have two principal objects. The one is to describe and differentiate the national parks in a manner which will enable the reader to appreciate their importance, scope, meaning, beauty, manifold uses and enormous value to individual and nation. The other is to use these parks, in which Nature is writing in large plain lines the story of America's making, as examples illustrating the several kinds of scenery, and what each kind means in terms of world building; in other words, to translate the practical findings of science into unscientific phrase for the reader's increased profit and pleasure, not only in his national parks but in all other scenic places great and small.

At the outset I have been confronted with a difficulty because of this double objective. The rÔle of the interpreter is not always welcome. If I write what is vaguely known as a "popular" book, wise men have warned me that any scientific intrusion, however lightly and dramatically rendered, will displease its natural audience. If I write the simplest of scientific books, I am warned that a large body of warm-blooded, wholesome, enthusiastic Americans, the very ones above all others whose keen enjoyment I want to double by doubling their sources of pleasure, will have none of it. The suggestion that I make my text "popular" and carry my "science" in an appendix I promptly rejected, for if I cannot give the scientific aspects of nature their readable values in the text, I cannot make them worth an appendix.

Now I fail to share with my advisers their poor opinion of the taste, enterprise, and intelligence of the wide-awake American, but, for the sake of my message, I yield in some part to their warnings. Therefore I have so presented my material that the miscalled, and, I verily believe, badly slandered "average reader," may have his "popular" book by omitting the note on the Appreciation of Scenery, and the several notes explanatory of scenery which are interpolated between groups of chapters. If it is true, as I have been told, that the "average reader" would omit these anyway, because it is his habit to omit prefaces and notes of every kind, then nothing has been lost.

The keen inquiring reader, however, the reader who wants to know values and to get, in the eloquent phrase of the day, all that's coming to him, will have the whole story by beginning the book with the note on the Appreciation of Scenery, and reading it consecutively, interpolated notes and all. As this will involve less than a score of additional pages, I hope to get the message of the national parks in terms of their fullest enjoyment before much the greater part of the book's readers.

The pleasure of writing this book has many times repaid its cost in labor, and any helpfulness it may have in advancing the popularity of our national parks, in building up the system's worth as a national economic asset, and in increasing the people's pleasure in all scenery by helping them to appreciate their greatest scenery, will come to me as pure profit. It is my earnest hope that this profit may be large.

A similar spirit has actuated the very many who have helped me acquire the knowledge and experience to produce it; the officials of the National Park Service, the superintendents and several rangers in the national parks, certain zoologists of the United States Biological Survey, the Director and many geologists of the United States Geological Survey, scientific experts of the Smithsonian Institution, and professors in several distinguished universities. Many men have been patient and untiring in assistance and helpful criticism, and to these I render warm thanks for myself and for readers who may benefit by their work.