Sometimes the goal is fabulous or mythical, but potent to lure, like the land of El Dorado, abounding in gold and jewels, which for two centuries spurred on Spanish exploration in America. Other than purely material motives may initiate or maintain such a movement, an ideal or a dream of good, like the fountain of eternal youth which brought Ponce de Leon to Florida, the search for the Islands of the Blessed, or the spirit of religious propaganda which stimulated the spread of the Spanish in Mexico and the French in Canada, or the hope of religious toleration which has drawn Quaker, Puritan, Huguenot, and Jew to America. It was an idea of purely spiritual import which directed the century-long movement of the Crusades toward Jerusalem, half Latinized the Levant, and widened the intellectual horizon of Europe. A national or racial sentiment which enhaloes a certain spot may be pregnant with historical results, because at any moment it may start some band of enthusiasts on a path of migration or conquest. The Zionist agitation for the return of oppressed Jews to Palestine, and the establishment of the Liberian Republic for the negroes in Africa rest upon such a sentiment. The reverence of the Christian world for Rome as a goal of pilgrimages materially enhanced the influence of Italy as a school of culture during the Middle Ages. The spiritual and ethnic association of the Mohammedan world with Mecca is always fraught with possible political results. The dominant tribes of the Sudan, followers of Islam, who proudly trace back a fictitious line of ancestry to the Arabs of Yemen, are readily incited to support a new prophet sprung from the race of Mecca.[211] The pilgrimages which the Buddhists of the Asiatic highlands make to the sacred city of Lhassa ensure China's control over the restless nomads through the instrumentality of the Grand Lama of Tibet. [Sidenote: Results of historical movement.] Historical movements are varied as to motive, direction, numerical strength, and character, but their final results are two, differentiation and assimilation. Both are important phases of the process of evolution, but the latter gains force with the progress of history and the increase of the world's population. [Sidenote: Differentiation and area.]