For those who would aspire to the gift of pure vision, and in whom the faculty is striving for expression, the following pages are written. To others we would say, Be content. All birds are not eagles. The nightingale has a song, the humming-bird a plumage which the eagle will never possess. The nightingale may sing to the stars, humming-bird to the flowers, but the eagle, whose tireless eyes gaze into the heart of day, is uncompanioned in its lofty loneliness in the barren mountain-tops.