Four salient groupings stand out among the brown peoples: India, Irán, "Arabistán," and "Turkestán." The last two words are used in a special sense to denote ethnic and cultural aggregations for which no precise terms have hitherto been coined. India is the population-centre of the brown world. More than 300,000,000 souls live within its borders--two-thirds of all the brown men on earth. India has not, however, been the brown world's spiritual or cultural dynamic, those forces coming chiefly from the brown lands to the westward. Irán (the Persian plateau) is comparatively small in area and has less than 15,000,000 inhabitants, but its influence upon the brown world has been out of all proportion to its size and population. "Arabistán" denotes the group of peoples, Arab in blood or Arabized in language and culture, who inhabit the Arabian peninsula and its adjacent annexes, Syria and Mesopotamia, together with the vast band of North Africa lying between the Mediterranean and the Sahara Desert. The total number of these Arabic peoples is 40,000,000, three-fourths of them living in North Africa. The term "Turkestán" covers the group of kindred peoples, often called "Turanians," who stretch from Constantinople to Central Asia, including the Ottoman Turks of Asia Minor, the Tartars of South Russia and Transcaucasia, and the Central Asian Turkomans. They number in all about 25,000,000. Such are the four outstanding race-factors in the brown world. Let us now examine that spiritual factor, Islam, from which the brown renaissance originally proceeded, and on which most of its present manifestations are based. Islam's warlike vigor has impressed men's minds ever since the far-off days when its pristine fervor bore the Fiery Crescent from France to China. But with the passing cycles this fervor waned, and a century ago Islam seemed plunged in the stupor of senile decay. The life appeared to have gone out of it, leaving naught but the dry husks of empty formalism and soulless ritual. Yet at this darkest hour a voice came crying from out the vast Arabian desert, the cradle of Islam, calling the Faithful to better things. This puritan reformer was the famous Abd-el-Wahab, and his followers, known as Wahabees, soon spread over the length and breadth of the Mohammedan world, purging Islam of its sloth and rekindling the fervor of olden days. Thus began the great Mohammedan Revival.