Economists tell us that the selling-value or price of any commodity is a function of its scarcity ; and we need no telling that artists and authors pay little attention to the economics of their work. They are lazy about it, because the marketing of their wares does not seem an attractive subject. How attractive are its principles, a little reflection will show. Samuel Butler had some interesting things to say on the relation of Art to Art Schools in Alps and Sanctuaries, and he suggested elsewhere that part of the education offered in these schools, if they were to be tolerated, should be a course of study in the prices of pictures at recent sales. There is something to be said for his view. Every collector studies sales ; and Robert Ross had instructive things to say about the value of attendance in the sale-room. Since, however, the course proposed by Butler, the example set by collectors, is not likely to be generally followed, criticism may seek briefly to define the conditions under which a maker, whether of pictures or of books, has to sell his wares, so that, by understanding these conditions, he may fulfil them to the best advantage.