To the first class belong the architectures of Egypt, Greece, and Gothic architecture as practised in the north of Europe; to the second belong Roman architecture of the splendid period, Moorish architecture, and Italian Gothic, so called. In the first class the bones of the building were also its flesh; in the second bones and flesh were in a manner separable, as is proven by the fact that they were separately considered, separately fashioned. Ruined Karnak, the ruined Parthenon, wrecked Rheims, show ornament so integral a part of the fabric--etched so deep--that what has survived of the one has survived also of the other; while the ruined Baths of Caracalla the uncompleted church of S. Petronio in Bologna, and many a stark mosque on many a sandy desert show only bare skeletons of whose completed glory we can only guess. In them the fabric was a framework for the display of the lapidary or the ceramic art--a garment destroyed, rent, or tattered by time and chance, leaving the bones still strong, but bare. This classification of architecture into Inherent and Incrusted is not to be confused with the discrimination between architecture that is _Arranged_, and architecture that is _Organic_, a classification which is based on psychology--like the difference between the business man and the poet: talent and genius--whereas the classification which the reader is asked now to consider is based rather on the matter of expediency in the use of materials. Let us draw no invidious comparisons between Inherent and Incrusted architecture, but regard each as the adequate expression of an ideal type of beauty; the one masculine, since in the male figure the osseous framework is more easily discernible; the other feminine, because more concealed and overlaid with a cellular tissue of shining, precious materials, on which the disruptive forces in man and nature are more free to act. It is scarcely necessary to state that it is with Incrusted architecture that we are alone concerned in this discussion, for to this class almost all modern buildings perforce belong. This is by reason of a necessity dictated by the materials that we employ, and by our methods of construction. All modern buildings follow practically one method of construction: a bony framework of steel--or of concrete reinforced by steel--filled in and subdivided by concrete, brick, hollow fire-clay, or some of its substitutes. To a construction of this kind some sort of an outer encasement is not only æsthetically desirable, but practically necessary. It usually takes the form of stone, face-brick, terra-cotta, tile, stucco, or some combination of two or more of these materials. Of the two types of architecture the Incrusted type is therefore imposed by structural necessity.