This essay is a new application to Lincoln cathedral in Gothic architecture, and to the Temple of Theseus in Greek architecture, of the principles of symmetrical beauty already so profusely illustrated and demonstrated by Mr Hay. The theory which Mr Hay has propounded in so many volumes is not only a splendid contribution towards a science of æsthetic proportions, but, for the first time in the history of art, proves the possibility, and lays the foundations of such a science. To those who are not acquainted with the facts, these expressions will sound hyperbolical, but they are most true. II. In royal 8vo, with Copperplate Illustrations, price 5s., THE NATURAL PRINCIPLES OF BEAUTY, AS DEVELOPED IN THE HUMAN FIGURE. _From the Spectator._ We cannot refuse to entertain Mr Hay’s system as of singular intrinsic excellence. The simplicity of his law and its generality impress themselves more deeply on the conviction with each time of enforcement. His theory proceeds from the idea, that in nature every thing is effected by means more simple than any other that could have been conceived,—an idea certainly consistent with whatever we can trace out or imagine of the all-wise framing of the universe. _From the Sun._ By founding (if we may so phrase it) this noble theory, Mr Hay has covered his name with distinction, and has laid the basis, we conceive, of no ephemeral reputation. By illustrating it anew, through the medium of this graceful treatise, he has conferred a real boon upon the community, for he has afforded the public another opportunity of following the golden rule of the poet—by looking through the holy and awful mystery of creation to the holier and yet more awful mystery of Omnipotence. _From the Cambridge Journal of Classical and Sacred Philology._ 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. III. In royal 8vo, with Copperplate Illustrations, price 5s., THE ORTHOGRAPHIC BEAUTY OF THE PARTHENON REFERRED TO A LAW OF NATURE. To which are prefixed, a few Observations on the Importance of Æsthetic Science as an Element in Architectural Education. _From the Scottish Literary Gazette._ We think this work will satisfy every impartial mind that Mr Hay has developed the true theory of the Parthenon—that he has, in fact, to use a kindred phraseology, both _parsed_ and _scanned_ this exquisitely beautiful piece of architectural composition, and that, in doing so, he has provided the true key by which the treasures of Greek art may be further unlocked, and rendered the means of correcting, improving, and elevating modern practice. _From the Edinburgh Guardian._