There are eight volumes of "Frederick the Great," containing, according to Barrett Wendell's computation, over one million words; and this eighteenth-century tale, with its large number of great and little characters, its "mass of living facts" impressed Wendell chiefly with its unity. "Whatever else Carlyle was," he wrote, "the unity of this enormous book proves him, when he chose to be, a Titanic artist."[23] Only those who have striven for unity in a narrative can appreciate the tribute contained in these words. It was a struggle, too, for Carlyle. Fifty-six years old when he conceived the idea of Frederick, his nervousness and irritability were a constant torment to himself and his devoted wife. Many entries in his journal tell of his "dismal continual wrestle with Friedrich,"[24] perhaps the most characteristic of which is this: "My Frederick looks as if it would never take shape in me; in fact the problem is to burn away the immense dungheap of the eighteenth century, with its ghastly cants, foul, blind sensualities, cruelties, and _inanity_ now fallen _putrid_, rotting inevitably towards annihilation; to destroy and extinguish all that, having got to know it, and to know that it must be rejected for evermore; after which the perennial portion, pretty much Friedrich and Voltaire so far as I can see, may remain conspicuous and capable of being delineated."[25] The student, who has become acquainted with the works of Gibbon, Macaulay, and Carlyle, will wish to know something of the men themselves and this curiosity may be easily and delightfully gratified. The autobiographies of Gibbon, the Life of Macaulay by Sir George Trevelyan, the History of Carlyle's Life by Froude, present the personality of these historians in a vivid manner. Gibbon has himself told of all his own faults and Froude has omitted none of Carlyle's, so that these two books are useful aids in a study of human nature, in which respect they are real adjuncts of Boswell's Johnson. Gibbon, Carlyle, and Macaulay had an insatiable love of reading; in their solitary hours they were seldom without books in their hands. Valuable instruction may be derived from a study of their lives from their suggestions of books, helpful in the development of a historian. They knew how to employ their odd moments, and Gibbon and Macaulay were adepts in the art of desultory reading. Sainte-Beuve makes a plea for desultory reading in instancing Tocqueville's lack of it, so that he failed to illustrate and animate his pages with its fruits, the result being, in the long run, great monotony.[26] As a relief to the tired brain, without a complete loss of time, the reading at hazard, even browsing in a library, has its place in the equipment of a historian. One of the most striking examples of self-education in literature is Carlyle's seven years, from the age of thirty-two to thirty-nine, passed at Craigenputtock where his native inclination was enforced by his physical surroundings.