The mosque of Cordova is superior, in respect to materials, to the other remaining Moorish buildings in Spain, in which plaster is used to excess. It is vain, however, to look in any of them for any distinct or novel constructional departure. The lintel and arch in Greece and Rome, the dome carried on pendentives in Byzance, were features giving character to each style, but the art of the Mahometan architects differed only in form and colour from its predecessors. The horseshoe arch with one and two centres, that is both round and pointed, was used by them almost exclusively, but it cannot rank as a constructional invention, for the real arch starts only at the level of the centres, and the remaining lower portion is a mere corbelling to obtain a form pleasing to the eye. Any new method of construction always affected the surrounding parts, and often altered the whole design of a building. It is obvious, therefore, that a mere change in the appearance of an arch such as this, which affects nothing connected with it, cannot be said to have created any new era in the progress of building. We hear the question frequently asked why a modern and new style is not developed in our times, and the answer architects make is illustrated by just this case, that is, that no new style can be evolved without a new constructive principle. As yet none such has been forthcoming, the only novel method of construction lately introduced being the employment of iron girders and posts, which, from an artistic point of view, can scarcely be considered an improvement upon the use of what are called the natural building materials. IX. THE ROMANESQUE STYLE. Some late historians have departed from the previously generally accepted nomenclature of architectural styles, in designating under the general term of Christian architecture all buildings erected between the tenth and sixteenth centuries in Western Europe. As, however, Christian building in Europe began with the conversion of Constantine, this chronology is hardly satisfactory, and as the customary division of Gothic from the styles preceding it, is on many grounds a convenient one, it is preferable to adopt the conventional names, and to distinguish under the title of “Romanesque” the outgrowth of the debased form of Roman architecture which, influenced by Byzantine and Arabic art, formed a distinct method of building throughout the West for nearly two centuries after the year 1000 A.D., giving it the alternative name of “Norman” in Normandy and England. Previous to this date the long continuance of war and barbaric incursions seem to have prevented the erection of any stable edifices; fire and the poverty of the material with which they were constructed having caused the destruction of the few of which an account has been preserved.