In pages 34, 35, and 58, I have reiterated an opinion advanced in several of my former works, viz., that, besides genius, and the study of nature, an additional cause must be assigned for the general excellence which characterises such works of Grecian art as were executed during a period commencing about 500 B.C., and ending about 200 B.C. And that this cause most probably was, that the artists of that period were instructed in a system of fixed principles, based upon the doctrines of Pythagoras and Plato. This opinion has not been objected to by the generality of those critics who have reviewed my works; but has, however, met with an opponent, whose recondite researches and learned observations are worthy of particular attention. These are given in an essay by Mr C. Knight Watson, “On the Classical Authorities for Ancient Art,” which appeared in the _Cambridge Journal of Classical and Sacred Philology_ in June 1854. As this essay is not otherwise likely to meet the eyes of the generality of my readers, and as the objections he raises to my opinion only occupy two out of the sixteen ample paragraphs which constitute the first part of the essay, I shall quote them fully:— “The next name on our list is that of the famous Euphranor (B.C. 362). For the fact that to the practice of sculpture and of painting he added an exposition of the theory, we are indebted to Pliny, who says (xxxv. 11, 40), ‘Volumina quoque composuit de symmetria et coloribus.’ When we reflect on the _critical_ position occupied by Euphranor in the history of Greek art, as a connecting link between the idealism of Pheidias and the naturalism of Lysippus, we can scarcely overestimate the value of a treatise on art proceeding from such a quarter. This is especially the case with the first of the two works here assigned to Euphranor. The inquiries which of late years have been instituted by Mr D. R. Hay of Edinburgh, on the proportions of the human figure, and on the natural principles of beauty as illustrated by works of Greek art, constitute an epoch in the study of æsthetics and the philosophy of form. Now, in the presence of these inquiries, or of such less solid results as Mr Hay’s predecessors in the same field have elicited, it naturally becomes an object of considerable interest to ascertain how far these laws of form and principles of beauty were consciously developed in the mind, and by the chisel, of the sculptor: how far any such system of curves and proportions as Mr Hay’s was used by the Greek as a practical manual of his craft. Without in the least wishing to impugn the accuracy of that gentleman’s results—a piece of presumption I should do well to avoid—I must be permitted to doubt whether the ‘Symmetria’ of Euphranor contained anything analogous to them in kind, or indeed equal in value. It must not be forgotten that the truth of Mr Hay’s