Their insult to Rome! What could be more humiliating than the circumstances under which it took place (A.D. 846)? An insignificant Saracen expedition entered the Tiber and appeared before the walls of the city. Too weak to force an entrance, it insulted and plundered the precincts, sacrilegiously violating the tombs of St. Peter and St. Paul. Had the city itself been sacked, the moral effect could not have been greater. From the church of St. Peter its altar of silver was torn away and sent to Africa--St. Peter's altar, the very emblem of Roman Christianity! Constantinople had already been besieged by the Saracens more than once; its fall was predestined, and only postponed. Rome had received the direst insult, the greatest loss that could be inflicted upon it; the venerable churches of Asia Minor had passed out of existence; no Christian could set his foot in Jerusalem without permission; the Mosque of Omar stood on the site of the Temple of Solomon. Among the ruins of Alexandria the Mosque of Mercy marked the spot where a Saracen general, satiated with massacre, had, in contemptuous compassion, spared the fugitive relics of the enemies of Mohammed; nothing remained of Carthage but her blackened ruins. The most powerful religious empire that the world had ever seen had suddenly come into existence. It stretched from the Atlantic Ocean to the Chinese Wall, from the shores of the Caspian to those of the Indian Ocean, and yet, in one sense, it had not reached its culmination. The day was to come when it was to expel the successors of the Caesars from their capital, and hold the peninsula of Greece in subjection, to dispute with Christianity the empire of Europe in the very centre of that continent, and in Africa to extend its dogmas and faith across burning deserts and through pestilential forests from the Mediterranean to regions southward far beyond the equinoctial line.