I have deliberated a long time about coupling some of my sketches of outdoor nature with a few chapters of a more purely literary character, and thus confiding to my reader what absorbs and delights me inside my four walls, as well as what pleases and engages me outside those walls; especially since I have aimed to bring my outdoor spirit and method within, and still to look upon my subject with the best naturalist's eye I could command. I hope, therefore, he will not be scared away when I boldly confront him in the latter portions of my book with this name of strange portent, Walt Whitman, for I assure him that in this misjudged man he may press the strongest poetic pulse that has yet beaten in America, or perhaps in modern times. Then, these chapters are a proper supplement or continuation of my themes and their analogy in literature, because in them we shall "follow out these lessons of the earth and air," and behold their application to higher matters.