Thoreau, the Concord stoic, is one of those writers who, indebted to civilization and the university for much culture, used that culture in fresh explorations of Nature. His books, peculiar in their structure, are the freshest and the best in their own department. He was, first of all, a naturalist. He outgrew society. He became a citizen of the forest. His books, in their very titles, show the spirit of the man. They are: “A Week on the Concord and Merrimack Rivers,” “Walden, or Life in the Woods,” “Excursions,” and “The Maine Woods.” Their contents are what their titles indicate. His “Week” is the record of an actual week's voyage upon those rivers; but its leisurely flow shows that the book was by no means written in a week or a month, but was the slow outcome of a thoughtful manhood. It is filled with the settled principles, facts, convictions of a man who is in his prime. The thoughts arise from his subject and range through religion, morals, society, literature, and the facts of humble life. His “Walden” shows how the retiring and determinate scholar may bury himself in the woods, and with a celibate life, may simplify his wants and divide his time equally between the exercise of muscle and of mind. It is a biography wholly unique, not so attractive nor surprising as Robinson Crusoe's, but to the inquiring few having a winning interest, which will always make it a classic in its kind.