Of all the literary terms in common use, the word “essay” has perhaps the widest field and the most indeterminate content. Since the form to which it applies has taken on a fresh character in the hands of almost all its chief exponents, it has become in practice the designation for any piece of prose of moderate length, and has consequently embraced a bewilderingly various subject-matter. Moreover, the essayists themselves are by no means all of a piece. Bacon and Lamb, for instance, have little in common; and the type of ‘essayist’ represented by Macaulay and Carlyle has little in common with either. As a result of this wide extension, studies of the essay either include so much as to be very indefinite, or else are based on partial views, the upshot, in either case, becoming sufficiently vague. At the same time, the word “essay” goes on being used, and collections, of curiously assorted content, go on being made; and it therefore seems worth while to pass in review the different types represented in actual practice, in order to see just how much continuity is discernible among them.