But in the seventy-one generations which separated Mohammed and Ishmael, a radical change of circumstances had befallen the rival branches of the house of Abraham. The descendants of Isaac, who had been promised the earth for an inheritance, now enslaved or exiled, and proverbial for bad faith, had become reviled and contemned of all men. On the other hand, from Ishmael the vagabond, deserted by his father and renounced by his kindred, had sprung a noble, valiant, and hospitable race, whose destiny was the promotion of civilization and the extension of empire. And in due time the latter, having obtained possession of the opulent regions of the East, tolerated the despised Hebrew only upon payment of tribute, and restricted him to a distinctive costume as a symbol of his degradation. He was compelled, in token of respect, to remove his slippers whenever he passed a mosque, and under penalty of the lash to kneel abjectly in the dust before the haughty Ishmaelite; while the capital of the land from which he had been banished, endeared to him by the memory of his sovereigns and the traditions of his faith, was in the power of his hereditary enemies, whose sacrilegious hands had raised the gilded dome of one of their proudest fanes upon the very spot long consecrated by the most revered associations of his race and his religion. The law of compensation, which controls the fate of man, was at last fulfilled, and retribution, if long delayed, was then exacted with relentless severity. The benefits wrought by Mohammedans--especially during the Middle Ages--have, until the end of the last century, been silently ignored or studiously depreciated by historians; in some instances through want of information, but, for the most part, because the phenomenal progress of Islam, when compared with the apathetic condition of other religions, suggested a formidable rivalry. But in this age, insatiable of knowledge and equipped with every means of obtaining it, it is no longer possible for clerical intolerance to obscure the splendid achievements of Moslem science. The day has long since past when the labors of astronomers like Ibn-Junis, of historians like Al-Makkari, of philosophers like Averroes, of physicians like Avicenna, and of botanists like Ibn-Beithar, can be treated with obloquy because they were not authorized by the decree of an Ecumenical Council or approved by a bull of his Holiness the Pope.