The _Liber Studiorum_ is an important aspect of Turner’s genius--so important that it seems to deserve a chapter to itself, even in so summary an investigation as the present. Yet from the point of view of its subject-matter, it is evident that the ‘Liber’ does not throw into relief any side of Turner’s art not amply illustrated in his paintings. What light the sequence of ‘Pastoral’ subjects throws upon the gradual development of his conception of realistic art, has already been touched upon in the previous chapter. But there remains one point of view from which it seems to me the ‘Liber’ possesses a special interest for our present study. In these designs we can study the formal elements of Turner’s art freed from the disturbing influence of colour. Each plate is primarily an arrangement in line and light and shade, and the requirements of what I may call melodic invention are considered before those of mere representation; that is to say, the emphasis is always on the subjective and constructive side of art, as opposed to its power of reproduction of the elements immediately given in ordinary perception. Especially important from this point of view are those subjects, generally amongst the earlier plates, in which considerable alterations were made during the course of execution. An examination of a few of the cases in which there are important differences between the first preliminary drawing and the completed engraving is certainly well within the limits of our present inquiry; and such comparisons are worth making for their own sake, as they bring out very clearly certain characteristics of all pictorial art, and especially of Turner’s, which are not easily grasped when our observations are complicated by the presence of colour. The first drawings executed for the work were made in October 1806, when Turner was on a visit to Mr. Wells, at Knockholt, in Kent. One of Mr. Wells’s daughters has told us that it was mainly on her father’s advice that Turner decided to undertake the work. But he required ‘much and long continued spurring’ before he could be induced to make a beginning. ‘At last,’ we are told, ‘after he had been well goaded, one morning, half in a pet he said, “Zounds, Gaffer, there will be no peace with you till I begin--well, give me a sheet of paper there, rule the size for me, tell me what I shall take.” The lady adds, ‘I sat by Turner laughing and playing whilst he made the drawings,’ ‘and before he left us the first five subjects which form the first number were completed and arranged for publication greatly to my dear Father’s delight.’ (The letter is given _in extenso_ in Mr. Rawlinson’s _Liber Studiorum_, 2nd edition, pp. xii and xiii.)