654 COMPARATIVE ARCHITECTURE. occupying the deserts west of the Euphrates. Its exact origin appears to be unknown, but it is generally taken as being derived from the Arabic " Sahva," a desert. The name was given to the followers of Mahomet, and is so used throughout this chapter irrespective of nationality. ii. Geological. — As the geological formation differed in each country, local materials and methods of building were employed, and marble, stone, brick, plaster and wood were all employed. Domes were frequently constructed of brick plastered externally and internally, or of stone, as in India. They were generally built in projecting horizontal courses, thus avoiding oblique pressure on the supporting walls. In Spain, brick and plaster were the principal materials responsible for the peculiar decorative surface treatment. In Northern and Central India, marble and red sandstone were available, and a more monumental type was evolved, richness in surface decoration being obtained by the inlay of precious stones. iii. Climate. — The buildings, being for the most part in Eastern or Southern climes, have small openings, and no large entrances or window surfaces, although a special treatment of monumental entrance gateways was evolved in India (Nos. 294 B, E, 295 and 297). Such features are always subservient to practical necessity and to climatic influences. iv. Religion. — The essence of the Mahometan faith — the last of the three great religions which have arisen from among the Semitic nations — is contained in the words from the Koran, "There is no God but God, and Mahomet is His prophet." The Koran was compiled by Mahomet (born a.d. 570, died 632), from the Bible, Talmud, Apocryphal Gospels, and other sources. Most of the states which embraced Mahometanism became independent, and only yielded nominal obedience to the Chief Caliph ; thus ifi Syria, Persia, Egypt, North Africa and Spain, independent Caliphs reigned, accentuating the differences of style. The prohibition in decoration and sculpture of the use of all natural objects, including the human and animal forms, probably led to the intricate form of geometrical surface decora- tion known as Arabesques, partly influenced by Byzantine art (Nos. 290 and 291). The Arab was a fatalist (Islam = God's will be done), to whom the present was everything, and such a condition often helped to the erection of buildings, not permanent in themselves, but decorated with pleasing forms and colors with poor materials, such as plaster. Local conditions and variety of temperament, however, affected such treatment, for in India and Egypt tomb houses of a permanent nature were constructed. Such tomb houses, as the Taj Mehal at Agra (Nos. 294 a, b, c,
