Persian architecture, after the Arab con quest was strongly influenced by the Sasanian palaces. The dome and vault, the colossal portal-arches and the use of brick and tile evi dence the Mesopotamian origin carried to Persia through the medium of Sasanian design. From Persia, the Mohammedan architecture of India received its inspiration and beginning in the 11th century there appears the growth of an Indo-Moslem architectural style char acterized by a grandeur and amplitude of dis position and a symmetry and monumental dignity which, contrasted with the Moresque style of the Arabs, awards every advantage to Indian work. The dome on a square plan was almost universal. The Byzantine pen dentive was not used, but in its place original combinations of vaulting surfaces of corbeling and ribs appear. Artistic settings for the monuments of this type are noted, and in the greatest of the Indian monu ments, the Taj Mahal at Agra, the style pos sesses a production in which constructive science combined with noble proportions and exquisite beauty is unsurpassed by any of the greatest architectural triumphs of the world. After the conquest of Constantinople in 1453, the Christian church of Hagia Sophia was occupied as the chief mosque and served as an official type to control Turkish mosque design in plan and constructive principle. Thus, out of the Jus tinian edifice, was developed a style of archi tecture less decorative and voluptuous than the style of Persia, Africa, or India, but neverthe less of great dignity. The. Turkish mosque, the Suleimaniyeh (1553), with its soaring min arets, serves as a Turkish type that governs to the present day.
The Dark Ages that fol lowed the fall of Rome (476 am.) constituted an experimental period during which the peoples of Europe were being Christianized and the influence of the Church was being established. Nations and individuals were groping for truth in government, religion and in life, and through out Northern Italy, the Rhine Provinces, Ile de France, Southern France, Normandy, and Nor man England, art in its various departments was called upon to express each stage of ad vance. Roman monuments existed in all parts of the Christianized regions, and these monu ments of antiquity, serving as constructive models, inspired a new architecture, modified by the liturgical requirements of the early Christians. This architecture, primarily based upon the Roman, varying in each province ac cording to the exigencies of climate, and the registration of racial characteristics in decora tive form and structural inventiveness, is known under the generic title of the Romanesque Style. In Tuscany, the churches were Basilican in plan with timbered ceilings and high clere story. In Lombardy, in the 11th and 12th cen turies the Basilican plans of classic Italy were translated into stone. Variations in plan re sulted from the necessities of the lithic prob lems. The naves were narrowed and instead of rows of columns carrying a high clere-story wall, as used in the Tuscan Romanesque churches, heavy piers connected by wide-spread ing nave arches supported the heavy ribs of the roof vaulting as in S. Ambrogio, Milan. Dur ing the 11th and 12th centuries in Northern and Western Europe, the church builders labored to adapt, like the Lombards in Italy, the Basili can plan to the requirements of vaulted con struction. Throughout France, Western Ger many, England and Belgium, the designers were constantly in trouble, caused by the diffi culty of building the round arched vault over the several portions of the churches. The thrusts of the clumsy vaults used to roof the nave were inadequately resisted by half barreled vaults over the side aisles, through the medium of which the strains of the great central vaults were transmitted to enormously heavy side walls. In these cases the clere-story necessarily disap peared and the lighting problem, which did not amount to much in the southern provinces, be came a serious consideration in the cloudy regions of the north. There it was necessary to raise the nave vault higher in order to in troduce clere-story windows. To accomplish the introduction of the clere-story windows groined vaults replaced the barreled vault. The introduction of the groined vault made possible the concentration of the roof thrusts upon a series of isolated supports or clustered piers.
The groined vaults were of two forms, four part and six-part. The four-part vault is per haps best typified in the church at Vezelay, France. The six-part vault was used in Nor mandy in the Abbaye aux Hommes and the Abbaye aux Dames built in the time of Wil liam the Conqueror. The use of the six-part vault in these churches, while making possible a higher clere-story, was an awkward expedient, for the division of the square vaulting bay into six parts by the diagonal groinings and a middle transverse rib, necessitated two nar row skew vaults meeting at the centre of the vaulting bay. Although an unsatisfactory de vice, this vaulting scheme was retained for a hundred years or more, and even after the adop tion of the pointed arch form, it was common in the 12th century churches, both in France and in England. In constructing these vaults, the various ribs were erected independently of the vaulting surfaces, a principle of construction which the Romans had used in their concrete vaults. The buttressing necessary to support the various vaulted roofs was mainly internal and unsatisfactory. Subsequent to the Norman conquest, 1066, church and abbey building was greatly stimulated. Typical of the period in England and expressing the two various phases of the Norman style in England, are the cathedrals of Durham (10%) and Ely (1107). The original vaulting scheme of Durham was borrowed from the six-part vault method employed in Normandy. The instability of the six-part Norman construction is evidenced by the fact that the early vaults at Durham were replaced by four-part Roman esque construction. The English churches differ from the Continental edifices in two particulars. First, a huge tower was usually erected over the crossing of the nave and the transept, and sec ondly, the western portals were not emphasized. At Ely there appears a notable variant from the Durham Norman style, due conjecturally, to the influence of the Tuscan Romanesque. At Ely a bascilican church was designed in which the graceful and elegant details of the Italian Pisan churches was replaced by the heavy forms of the Norman ,art used not in a structure hut, a wholly decorative manner. A timber ceiling was used instead of stone vaults. This phase of the English Norman is prac tically nothing more than the Italian Basilica with a Norman envelope. In Germany a few churches dating back to the 9th century, in great part rebuilt, express the character of this period in that region. The church at Aix la-Chapelle in Prussia has been greatly altered, but it was without a doubt inspired by that of San Vitale at Ravenna. The Byzantine type here shown was repeated in a number of later churches. The conventual church at Hechingen, near Stuttgart, and at Quedlinburg, Saxony, exhibited quasi-classical sculpture with scroll work and elaborate mouldings. Groined vaults, low and narrow, are used. The same timidity and lack of stability in vault construction is apparent here as in other parts of Europe. The great cathedral of Speyer, Bavaria, and the church at Gernrode belong to the 12th century, as do the church of Saint Michael at Hildesheim, the cathedral of Mayence, and the cathedral at Worms. These churches have been practically unchanged since the time of their building, and exhibit perhaps the most efficient examples of the Romanesque style. The Romanesque influence expresses itself in the far north in the cathedral of Lund in Sweden with the characteristics of the architecture of the period. The Scandinavian Peninsula depended for the most part upon timber for its construction and upon elaborate carving for its decoration. In Spain the Moors dominated the larger part of that country during the Romanesque era, but after the capture of Toledo (1062) by the Christians, there was a recession of Moorish influence, and in the northern provinces of Spain a number of im portant churches were erected which reflected the influence of French Romanesque models. Tlie Church of Saint Tag at Compostella is typical of these Spanish Romanesque edifices. Barrel vaults over the nave, groin vaulting over the side aisles, follow the precedents of France. In the employment of a dome or cupola, as in the old cathedral at Salamanca, over the cross ing of the nave and transepts is exhibited a characteristic departure from the French types.