the modern shops which are supposed to stand on sheets of plate glass), and its whole exterior appearance ought to be in accordance with, and convey the idea of, the manner and principle on which it is constructed.  The most important portions of the interior must be shown as such externally by the greater elaboration and emphasis of their architectural treatment.  If the general arrangement of the plan is symmetrical, on either side of a center (which, however, it cannot often be except in the largest type of monumental or public buildings), the architectural treatment must be symmetrical.  If the building is necessarily arranged, in accordance with the requirements of the plan, unsymmetrically, the architectural treatment must follow suit, and the same principle must be carried out through all the details.

Now this dependence of architectural design upon plan and construction is one of the conditions which is often overlooked by amateurs in forming a judgment upon architectural design; and the overlooking of this is one reason of the uncertainty of opinion about architecture as compared with such arts as sculpture and painting.  Few people know or care much about the structure and planning of buildings except those whose business it is to care about this; and consequently they do not realize what it is which they should look for in the architectural design.  They like it or do not like it, and they regard this as what is called a mere question of taste, which, according to the proverb, is not to be disputed about.  In fact, however, the good or bad taste of an architectural design, say, if you like, its correctness or incorrectness, is to a considerable extent a matter of logical reasoning, of which you must accurately know the premises before you can form a just conclusion.  But there is another reason for this prevalent uncertainty and vagueness of opinion, arising out of the very nature of architectural art itself, as compared with the imitative arts.  A painting of a figure on a landscape is primarily a direct imitation of the physical facts of nature.  I do not for a moment say it is only that, for there is far more involved in painting than the imitation of nature; but the immediate reference to nature does give a standard of comparison which to a certain extent every eye can appreciate.  But architecture is not an art which imitates natural forms at all, except as minor decorations, and it then does so, or should do so, only in a conventionalized manner, for reasons which we shall consider later on.  Architecture is, like music, a metaphysical art.  It deals with the abstract qualities of proportion, balance of form, and direction of line, but without any imitation of the concrete facts of nature.  The comparison between architecture and music is an exercise of the fancy which may indeed be pushed too far, but there is really a definite similarity between them which it is useful to notice.  For instance, the regular rhythm, or succession of accentuated points