But it may be said that these instances are from such obscure epochs that it is uncertain how far it was religion which acted on civilization. Let us, then, take one or two instances, concerning which there is less uncertainty. In the deserts, and among the vast plains of the Arabian Peninsula, a race had slumbered inactive for twenty centuries. Those nomad-Semitic tribes had wandered to and fro, engaged in perpetual internecine warfare, fulfilling the prediction concerning Ishmael, "He will be a wild man; his hand will be against every man, and every man's hand against him." No history, no civilization, no progress, no nationality, no unity, could be said to exist during that long period among these tribes. At length a man comes with a religious idea, a living, powerful conviction. He utters it, whether man will bear or forbear. He proclaims the unity and spirituality of God in spite of all opposition and persecution. At last his idea takes hold of the soul of this people. What is the result? They flame up into a mighty power; they are united into an irresistible force; they sweep over the world in a few decades of years; they develop a civilization superior to any other then extant. Suddenly there springs up in their midst a new art, literature, and science. Christendom, emasculated by an ecclesiastical and monastic Theology, went to Islam for freedom of thought, and found its best culture in the Mohammedan universities of Spain. Bagdad, Cairo, Damascus, Seville, Cordova, became centres of light to the world. The German conquerors darkened the regions they overran: the Mohammedans enlightened them. The caliphs and viziers patronized learning and endowed colleges, and some of their donations amounted to millions of dollars. Libraries were collected. That of a single doctor was a load for four hundred camels. That of Cairo contained a hundred thousand manuscripts, which were lent as freely as those in the Boston Public Library. The College Library of Cordova had four hundred thousand. In these places grammar, logic, jurisprudence, the natural sciences, the philosophy of Aristotle, were taught to students who flocked to them from all parts of Christendom. Many of the professors taught from memory: one man is reported to have been able to repeat three thousand poems. The Saracens wrote treatises on geography, numismatics, medicine, chemistry, astronomy, mathematics. Some, like Avicenna, went through the whole circle of the sciences. The Saracens invented pharmacy, surgery, chemistry. Geber, in the eighth century, could prepare alcohol, sulphuric acid, nitric acid, corrosive sublimate, potash, and soda. Their astronomers measured a degree of the earth's meridian near Bagdad, and determined its circumference as twenty-four thousand miles. They found the length of the year, and calculated the obliquity of the ecliptic. Roger Bacon quotes their treatises on optics. Trigonometry retains the form given it by the Arabs, and they greatly improved