His voluminous manuscript _Journal_ is an almost daily record of his observations of nature, mingled with his thoughts, from the time when he left college until his last sickness. At periods for nearly fifty years after his death, various works have been compiled from this _Journal_. The volumes published under the titles, _Early Spring in Massachusetts_ (1881), _Summer_ (1884), _Winter_ (1887), _Autumn_ (1892), and _Notes on New England Birds_ (1910) were not arranged by him in their present form. Editors searched his _Journal_ for entries dealing with the same season or type of life, and put these in the same volume. Sometimes, as, for instance, in _Winter_, paragraphs separated by an interval of nineteen years in composition become neighbors. In spite of the somewhat fragmentary nature of these works, lovers of Thoreau become intensely interested in them. His _Journal_ in the form in which he left it was finally published in 1906, in fourteen volumes containing 6811 printed pages. He differs from the majority of writers because the interest in his work increases with the passing of the years. GENERAL CHARACTERISTICS.--Thoreau's object was to discover how to live a rich, full life with a broad margin of leisure. Intimate companionship with nature brought this secret to him, and he has taught others to increase the joys of life from sympathetic observation of everyday occurrences. A mere unimaginative naturalist may be a bore; but Thoreau regarded nature with the eyes of a poet. His ear was thrilled with the vesper song of the whippoorwill, the lisping of the chickadee among the evergreens, and the slumber call of the toads. For him the bluebird "carries the sky on its back." The linnets come to him "bearing summer in their natures." When he asks, "Who shall stand godfather at the christening of the wild apples?" his reply shows rare poetic appreciation of nature's work:-- "We should have to call in the sunrise and the sunset, the rainbow and the autumn woods and the wild flowers, and the woodpecker and the purple finch and the squirrel and the jay and the butterfly, the November traveler and the truant boy, to our aid." He is not only a poet-naturalist, but also a philosopher, who shows the influence of the transcendental school, particularly of Emerson. Some of Thoreau's philosophy is impractical and too unsocial, but it aims to discover the underlying basis of enchantment. He thus sums up the philosophy which his life at Walden taught him:-- "I learned this at least by my experiment--that if one advances confidently in the direction of his dreams, and endeavors to live the life which he has imagined, he will meet with a success unexpected in common hours.... If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them."