But to some extent it is to the example of these specialists that must also be ascribed the skill in sea painting that, as time went on, was attained by many of their contemporaries who did not deal systematically with this class of subject. The habitual landscape painter, accustomed to fixed forms and effects that followed more or less regular rules, might easily have drifted into a conventional representation of the sea if he had not been shown the way to look at it by the men who knew it intimately, and if works by these men had not existed to provide him with the means of testing his own achievement. For his own credit, however, he had to strive to compete with them in knowledge of the sea, and had to measure an understanding of it acquired by deliberate and conscious effort against theirs which had been obtained by prolonged and personal contact; and to uphold his reputation as a painter of capacity he had to prove that he could grasp the essentials of whatever type of material he might elect to handle. Therefore, the adoption of a convention, the inadequacy of which could have easily been demonstrated, would have been a confession either of want of conscience or of deficient intelligence, and would have reflected upon his claim to rank as an artist of distinction. That is why at the end of the eighteenth century and the beginning of the nineteenth the number of men who, without specializing in the subject, painted the sea with undeniable ability, had become considerable. By that time artists were moving about much more freely in search of motives, and many of them made frequent visits to the coast with the particular intention of mastering the problems of sea painting, and of studying at first hand phases of nature which were to them comparatively new. Moreover, the interest taken by the public in sea pictures had grown in a marked degree, and there was a demand which the popular artist was called upon to satisfy. So most of the landscape men alternated regularly between inland views and coast scenes, and painted both with the same sincerity and the same strength of purpose. Constable, David Cox, De Wint, Copley Fielding, Edward Duncan, J. S. Cotman--to quote a few of the more notable names--added important records of sea and coast subjects to the list of their more memorable productions; and there was, of course, Turner, who might with justice be claimed as the greatest of all marine painters despite the fact that his sea pictures make up only a small proportion of his total achievement.