_System of Proportion_ It is customary, when any of the orders of Architecture are employed, to adopt a system of proportions which has been evolved from the best traditions of the past, and is generally accepted as the most satisfactory. Naturally these proportions are subject to modification to suit special conditions or personal treatment. According to the academic method, the diameter of the column is divided into two parts, which are called Modules, and each of these is again subdivided into thirty divisions called parts. This gives a scale by means of which all dimensions of height and projection are obtained. Since the diameter of the column forms the standard of measurement, the proportions of the relative parts are constant and in no way influenced by the size of the structure. This method, although very complete, is--owing to its multiplicity of dimensions--somewhat laborious in practice, and the method here proposed in its stead, though not claimed to be exact, will yet be found to be sufficiently accurate for ordinary requirements. It is proposed to deal here with the orders commonly employed in Renaissance architecture. These were based by the early exponents of the style on Roman examples. The Doric selected is that of Vignola, and is a refined version of the order used in the Theatre of Marcellus at Rome. The Ionic closely resembles the Roman Ionic order in the same building. The Corinthian is the Roman example from the Pantheon. _The Order_ An Order consists of a vertical column and a horizontal entablature, while in some instances the column rests on a pedestal. It is desirable before dealing with proportions to enumerate the various parts of which an order is composed. The column consists of a shaft, base and capital. The shaft is circular on plan and invariably tapered. The base is composed of mouldings, which are circular on plan, and a rectangular block or plinth. The capital is circular on plan, and in the Doric and Corinthian orders is divided from the shaft by a necking moulding. The capital is surmounted by a feature known as the abacus, which is rectangular on plan, but varies in detail in the different orders. Columns may be isolated or engaged, that is, built into walls so that they form projections from the surface. [Illustration: No. 153. Doric Order with Pedestal.] The pilaster is always engaged, and is rectangular on plan, but otherwise it has the same general features and proportions as the column. The entablature is the superstructure supported by the columns. It consists of an architrave, which is the lowest part, a frieze, the intermediate part, and a series of projecting mouldings known as the cornice. The pedestal, which occasionally forms a support for the columns, consists of a plinth, die and capping. The lower part or plinth is separated from the die by mouldings, and the capping is a projecting course of mouldings forming a simple cornice.