In the two works last mentioned, _Eastern Life_ and _The Thirty Years' Peace_, it seems to me that she touched the high-water mark of her permanent achievements. We have nearly reached the end of the long catalogue of her books, though by no means the end of her writings. Very much more work she did in her life, as will presently be told, but it was that kind of work which is (with the single exception of oratory) the most powerful at the moment, but the most evanescent--journalism. She was soon to begin to apply her ripe wisdom and her life-long study of the theory of government to the concrete problems of practical politics. The influence of an active and powerful journalist cannot be measured; the work itself cannot be adequately surveyed and criticized; and thus what is, perhaps, the most useful, capable and important work which Harriet Martineau did, eludes our detailed survey. We can best judge what was her power as a leader-writer and review and magazine essayist by noting how progressively her mind improved, and to what a high moral and intellectual standpoint she had attained in her latest volumes, just before she exchanged such sustained labors for the briefer though not less arduous efforts of leading and teaching through the periodical press. _The History of the Peace_ was completed in 1850, and was so immediately successful that the publisher asked Miss Martineau to write an introductory volume on the history of the first fifteen years of this century. While at work upon this "Introduction" she did also some short articles on various subjects for Charles Dickens' periodical, _Household Words_, and was likewise proceeding with the preparation of another volume of a very different kind. This last was published in January, 1851 (before the introductory volume of the _History_), under the title of _Letters on the Laws of Man's Nature and Development_, by Henry George Atkinson, F.G.S., and Harriet Martineau.