Of the Romans it may be said, “Mutant quadrata _rotundis_,”—circular forms and curves displaying themselves not only in elevation and section, but in plan; and while, among the Greeks, Architecture was confined almost exclusively to external appearance and effect, in the hands of the Romans it was made to minister to internal display of the most enchantingly picturesque kind, as would be amply attested by the Pantheon alone. In that edifice, and Hadrian’s Mausoleum (now barbarized into the Castello di S. Angelo), the cylindrical form was exhibited upon an imposing scale; in the Temple at Tivoli, in far lesser dimensions, but with most captivating taste; and again in the Tomb of Cæcilia Metella, we have a fine example of an unbroken _astylar_ circular mass. In such structures as the Colosseum and other Roman Amphitheatres, a different form of curvature, namely, the ellipsis, was employed with admirable propriety and effect. In interiors, again, we find the hemicycle or concave semicircular form both frequently and variously applied by the Romans in such edifices as their Baths, which afford many excellent studies for combinations of _plan_. To enter into the system of Roman Architecture as the subject itself would require, would very far exceed our present purpose and limits; much less can we pretend to treat here of the still more varied and complex Italian or Modern-European system, into which _fenestration_ so largely enters, _columniation_ being, more frequently than not, subordinate. Were we to touch upon the last-mentioned style and its various elements, it could be only so superficially as to be more disappointing than instructive. Better that the reader should admire our forbearance than complain of our unsatisfactory jejuneness. We may, however, permit ourselves to throw out one or two general remarks; the first of which is, that it is a great error to confound with the Italian the two Ancient Classical styles, applying to them alike the epithet ‘Grecian,’ merely in contradistinction to Gothic or Mediæval Architecture. It is absurd, too, to pretend to test by the Greek style, one so totally differently constituted as the Italian; an error that could hardly have been fallen into but for the practice of applying the same names to very different things. The term ‘Order’ has quite a different meaning, as applied to the original classical mode of the Art, from what it has in the other. In Italian composition, an Order is more frequently than not, mere decoration in the shape of columns and entablatures, fashioned _secundum artem_ (a very different thing from _artistically_), so as to resemble in detail and certain conventional distinctions those of the Ancients. Infinitely better would it have been, if, instead of allowing themselves to be misled by the pedantry of Vitruvius, the Architects of the so-called Revival, who showed much happiness of invention in other respects, had treated