Lombards conquered the greater part of the Byzantine Empire.

The Byzantine Empire finally fell at the hands of Mohammed II, and Constantinople became the Moslem capital in 1453, half a century after the beginning of the period of the Renaissance in Italy.

From 900 to 1200 Italy was to some extent the battlefield of ambitious European nations, suffering many invasions and constant unrest.

From 1200 to 1400 such Italian cities as Venice, Genoa, and Florence grew steadily in prosperity and power, mostly through commerce.

There was no national Italian government at this time, the balance of power being diplomatically adjusted by five united parts: the Duchy of Milan, the two nominal "republics" of Venice, the Papal States (centred at Rome) and the Kingdom of Naples.

The dates of the great periods of the Italian Renaissance are given as follows:

Early Renaissance, Florentine.... 1400-1600

The years and periods covered by the foregoing dates, from the fall of Rome to the close of the Italian Renaissance, saw greater developments in architecture than any subsequent span of time. Great as were these developments, however, it is necessary here to deal with them in the briefest possible manner, pointing out such salient points as will later prove an aid in distinguishing the architectural derivations of to-day.

Byzantine and Romanesque architecture flourished at about the same time, and were preceded by what is known as "Early Christian" architecture in Rome. As the Christians, at the beginning of the Christian Era, were neither rich nor powerful, their architectural efforts were, of necessity, restricted.

It was at this time that the idea of a "temple," or abode of deity, gave place to the idea of a "church," or place of worship for the devout. The temple, while a shrine, had been regarded more as a divine abode. The people came to offer prayer to their god in the temple. In the church, the devout assembled to make prayer, and an Invisible God came to them.

Gradually the architectural efforts of the early Christians began to assume certain definite forms: "Romanesque" in Italy proper, or the "Western Empire of Rome," and "Byzantine" in Byzantium (Constantinople), the "Eastern Empire of Rome."

Byzantine architecture was at its height under the Emperor Constantine, when he removed the capital from Rome to Constantinople, and the term covers not only the buildings actually erected in the Byzantine Empire at this time, but several important contemporary buildings in Italy.

Most notable of all Byzantine architectural monuments is the Church of St. Mark, in Venice. It was largely built from 1061-1071 A.D., with additions of columns and marble mosaics, between 1100-1350.

The second great monument of Byzantine architecture is the Church of Ste. Sophia, in Constantinople, so long now a Mohammedan Mosque. Ste. Sophia is of earlier date than St. Mark, having been built by the Byzantine Emperor Justinian in 532-537 A.D.

Both buildings, however, illustrate the most salient characteristics of Byzantine architecture.

The principal structural difference between Byzantine and Romanesque architecture is that the first developed the dome, while the second developed the vault. Byzantine architecture stopped at the dome-Romanesque architecture grew into the elaborate vaulting systems of the Gothic style.

The architectural "orders" of the Romans gave place to different forms in works of the Byzantine builders. Byzantine buildings were mostly of brick, embellished with mosaic, and depending for large effect on the dome; for detailed effect on colour. Arches were used structurally, springing from a different sort of column than those of the Greeks or Romans. The Byzantine column was usually short, and often placed in pairs, and the capitals were basket-shaped, effecting a transition from the arch to the cylindrical shaft of the column. These capitals were intricately carved, in a richly decorative manner, with conventional foliation or grotesque heads and animal forms.

In place of the mouldings and carvings of the Classic architects, the exteriors of Byzantine churches were diversified by horizontal bands of vari-coloured brick, as well as by the interest afforded by successive recessed arches.

Statuary formed no feature of this architecture, since the early Christians allowed nothing so reminiscent of pagan religions and pagan deities, or "idols' to be a part of their creed.

The art of mosaic work, both in coloured marbles and mosaic glass, reached its height in Byzantine architecture.

Church plans were usually in the form of a Greek

cross, with the dome covering the central part. In comparison with Romanesque and, later, Gothic church plans, those of the Byzantine churches were square and compact.

The dome, essentially an Eastern, or Asiatic form, has naturally come to be regarded as characteristic of Saracenic or Moorish architecture, with which, indeed, Byzantine has much in common.

Romanesque architecture was practised not only in churches erected in Italy, but spread through France and Germany as well. In certain details it was influenced to a considerable extent by Byzantine feeling, while structurally it was essentially different.

Instead of the dome construction of the Byzantine architects, the Romanesque church builders addressed all their efforts to the development of the vault as a method of roofing-their efforts culminating in the Gothic style of the Thirteenth Century.

The Romanesque church plan assumed much of the character of the later church and cathedral plans, consisting of a long central nave, flanked by narrower side-aisles, the nave terminating in the sanctuary and altar-the apse of the later cathedral plan. In order to support the heavy tile roof of the Romanesque church, it was necessary to develop masonry vaulting to a degree never before attempted, and "rib-vaulting," the basis of Gothic architecture, was evolved.

By way of definition, a plain vault, or "barrel" vault, is nothing more than a continuous arch-a roofing in the form of an inverted half-cylinder, supporting its own weight, as well as any superincumbent weight, on the principle of the arch (Fig. 1).

When two plain vaults intersect (Fig. 2), their

self-sustaining or supporting power is not impaired, and a new line is formed by the intersection ("AB," Fig. 2). This intersection is known as the "groin" of the vault, and the building of intersecting vaults was practised extensively by the Romans.

The later Romanesque builders, however, went a step further. They discovered that the only structurally essential members of the intersecting vaults were the groins, or stones forming the intersection. These, they found, would stand alone, independently

BARREL VAULT GROIN VAULT SINGLE RIB VAULT of the rest of the vault, so that lighter stones or brick might be used to fill in.

It is easy to see how this discovery led to the development of "rib-vaulting" (Fig. 3), in which the bones of the construction, so to speak were the groins of intersecting vaults-the vaults themselves becoming of secondary significance and of importance chiefly, to effect a symmetrical and finished" interior.

On this evolution of Romanesque architecture, the discovery of the structural sufficiency of vaulting ribs, rests the whole principle of Gothic architecture, for the intersection of vaults varying in height naturally brought about the discovery of the pointed arch.

About these two structural facts the genius of