The rise of Islam is an extraordinary phenomenon. In one generation the Arab is a wanderer, half patriarch, half brigand, pasturing his flocks on the verge of the cultivated lands of more civilized peoples, and snatching such prey as hazard brought within his grasp; in the next he is a conqueror ruling from the Indian Ocean to the Atlantic, and threatening to extinguish Christendom. On the vanquished he imposed his religion and his social code; he had no art to impose. Having become by force of conquest and the exigencies of government a dweller in cities, he showed his incapacity to understand the work of his predecessors in such eccentricities as re-erecting their fallen buildings with the columns inverted, using the capital as base, and the base in the capital’s place. As architects he employed the natives of the countries he had overrun, in Egypt Copts and Greeks, who reproduced Byzantine forms and fixed the typical lines on which the development of “Arab art” was to take place. In this deference to local tendencies is to be found the origin of the wide divergencies of art in the Mohammedan world,—of Persian art in the east, and Moorish art in the west. The conquered and converted peoples continued to build, as far as the main plan was concerned, in the same way as they had built before their conversion, adapting their previous methods to present needs, and to the requirements of their conquerors. In Barbary the development of art followed closely that of Spain. The Moorish art of Spain was chiefly Roman or Byzantine in origin; the first mosque built, that of Cordoba, is said to have been designed by architects from Byzantium. Columns used in its construction were brought from the ruins of Merida and other Roman towns, and even from distant parts of the Mediterranean. From this commencement sprang the later glories of Moorish art, exhibited in their most splendid developments at Granada in Spain, and Tlemçen in Algeria.