Lecturing, after the example set chiefly by Coleridge and Hazlitt, was at this time a favourite resource for those men of letters whose line of composition was not of the gainfulest; and Carlyle delivered several courses, some of which are unreported while others survive only in inadequate shapes. But _Heroes and Hero-Worship_ was at first delivered orally, though it was not printed till 1841; and about the same time, or rather earlier, appeared the _Miscellaneous Essays_--a collection of his work at its freshest, least mannered, most varied, and in some respects best. _Chartism_ (1839) and _Past and Present_ (1843) reflected the political problems of the time and Carlyle's interest in them. But it was not till 1845 that a second, in the ordinary sense, great work, _Oliver Cromwell's Letters and Speeches_, was published. Five years passed without anything substantive from him, but in 1850 appeared _Latter-Day Pamphlets_, the most brilliantly satiric, and in 1851 the softest, most finished, and (save theologically) least debatable of all his books, the exquisite biography in miniature called the _Life of Sterling_. Then he engaged, it is difficult to say whether by ill-luck or not, on the last and largest of his great single undertakings, the _History of Frederick the Great_. Fourteen years were passed, as a matter of composition, in "the valley of the shadow of Frederick," as his wife put it: half the time (from 1858 to 1865) saw the actual publication. Shortly after the completion of this, Carlyle visited Edinburgh to receive the Lord Rectorship of his University, and soon after his wife died. He survived her fifteen years, but did nothing more of great importance; indeed, he was seventy-one when this loss happened. Some short things on "John Knox," on "The Early Kings of Norway," and a famous letter on "Shooting Niagara" (the Reform Bill of 1867), with a few more, appeared; but he was chiefly occupied (as far as he was occupied at all) in writing reminiscences, and arranging memorials of Mrs. Carlyle. The publication of these books after his death by the late Mr. Froude led to a violent conflict of opinion both as to the propriety of the publication and as to the character of Carlyle himself.