The one external consideration by which decoration is limited is the material of which it is formed, and to the nature of which it must give full expression. In doing this it becomes inseparable from the building— not a merely accidental extraneous part of it, but a part of the essence which, with the body of the work, constitutes the art-creation. This consideration of the nature of the material necessitates the more or less extensive changes which have to be made in the original conception in order to make it conform to the given style. In ornamentation, as in proportion, there are most marked differences between the language of forms of different nations. Upon the range of their fancy, itself depend ent upon their grade of culture, depend the number of their conceptions and the kind and grade of their style.
Color in Archileaurc.—Our attention has thus far been occupied with the creation of form, but form never appears unaccompanied by color, and this latter element perhaps impresses the mind of the spectator even more than form. Thus Architecture has to deal not only with form, but also with color, which has especial influence in the more ideal part of the problem. In the choice of materials attention must be paid not only to their constructive suitability, but also to their harmony of color. When the choice of materials is not free and their colors do not harmonize with the general character of the building, the care bestowed upon construc tion and proportion must be doubled, so that the inharmonious character of the materials may be overcome, or, at least, diminished.
One of the chief problems in the choice of constructive materials is so to arrange them that their tints may be in harmonious relation with the idea of the building. Color also influences the constructive detail, since the shadows cast by bright materials are in stronger contrast than those cast by dark ones, and those cast by delicate tints contrast more strongly than those cast by deep ones; so that proportions do not appear of equal mass for all colors. It often occurs that, color excepted, all the other qualities of the materials are perfect.
As the raw material needs much preparation and must be brought into artistic form before it is capable of architectonic expression, so also the natural coloration is not always adapted to the representation of an archi tectural idea, and we must use an artificial scheme of coloration which can be applied locally to individual parts in order to give proportion, just as variety gives form. The effects of proportion given to the members of a building by colors, though they speak out sharply, are limited in their range; yet it is possible by means of color to denote the difference between heavy and light, supporting and supported structures—to tone down a rough form or to detach from one another forms which are not sufficiently distinct.
The principal use of color is, however, to bring out the decoration. Surfaces may be relieved by a rich play of colors without actual relief, and ideas may be with facility expressed by colors when the object they embellish calls for the widest possible range of imagination and fancy. color has its own province, and to a certain extent its own series of forms, and must therefore be treated in its own manner. A harmonious interplay of colors, with correct proportion in the distribution of each, is characteristic of a fine work of art. In a truly artistic period color has never made use of artificial shadows to bring out artificial reliefs and depths, nor has it in any way been employed as a makeshift for form.
Conchtsion.—We must content ourselves with the foregoing outline of the theory of Architectonics. As to the practice which is based on it— that is, the methods of solving according to its rules each individual prob lem, of proceeding rationally in the arrangement of every kind of build ing, of constructing various parts, as walls, windows, doors, halls, pillars, etc.—we can the less consider it in this connection, inasmuch as no the ory of the development can be traced in the history of art. We mentioned above that the laws of Nature often oppose one another, and that, as a clear result of a single one does not thus appear, forms are produced which the eve does not recognize as normal, but as freaks of Nature.
We find also in the history of art that the rational theory does not always dominate, but that, as in culture itself, all kinds of influences which may be external and unavoidable or may arise from deficient per ception or false guidance make themselves felt. We have dwelt partic ularly on man's imperfect conception of the general laws of artistic cre ation and of his misunderstanding of their application to a particular case, and this forms an almost fundamental law the operation of which prevents the untrammelled exercise of the ideal laws of Architecture. This does not result entirely from the individuality of the creative artists, but partly from the degree of culture possessed by the entire nation; and so by the side of the authority of theory appears the influence of tradition, which operates even more powerfully and has in a most conspicuous manner impressed itself upon the history of Art. The influence of tradition as it grew up with the nations has contributed more to the diversity of architectural styles than have the external necessities of climate. But all this can be dealt with only in a historical manner, and we shall there fore, when we treat of individual styles, make it our especial duty to dis cover how far the theories traced above have made themselves felt at all periods and iu various climes.