“From this thunderbolt we may date the consummation of the schism. It was enlarged by each ambitious step of the Roman pontiffs; the emperors blushed and trembled at the ignominious fate of their royal brethren of Germany; and the people were scandalized by the temporal power and military life of the Latin clergy.”[99] CHAPTER III THE FIRST CRUSADE Until the mechanical arts have advanced far enough to cause the attack in war to predominate over the defence, centralization cannot begin; for when a mud wall can stop an army, a police is impossible. The superiority of the attack was the secret of the power of the monied class who controlled Rome, because with money a machine could be maintained which made individual resistance out of the question, and revolt difficult. Titus had hardly more trouble in reducing Jerusalem, and dispersing the Jews, than a modern officer would have under similar circumstances. As the barbarians overran the Roman provinces, and the arts declined, the conditions of life changed. The defence gained steadily on the attack, and, after some centuries, a town with a good garrison, solid ramparts, and abundant provisions had nothing to fear from the greatest king. Even the small, square Norman tower was practically impregnable. As Viollet-le-Duc has explained, these towers were mere passive defences, formidable to a besieger only because no machinery existed for making a breach in a wall. The beleaguered nobles had only to watch their own men, see to their doors, throw projectiles at the enemy if he approached too near, counter-mine if mined, and they might defy a great army until their food failed. Famine was the enemy most feared.[100] By the eleventh century these towers had sprung up all over the West. Even the convents and churches could be defended, and every such stronghold was the seat of a count or baron, an abbot or bishop, who was a sovereign because no one could coerce him, and who therefore exercised all the rights of sovereignty, made war, dispensed justice, and coined money. In France alone there were nearly two hundred mints in the twelfth century. Down to the close of the Merovingian dynasty the gold standard had been maintained, and contraction had steadily gone on; but, for reasons which are not understood, under the second race, the purchasing power of bullion temporarily declined, and this expansion was probably one chief cause of the prosperity of the reign of Charlemagne. Perhaps the relief was due to the gradual restoration of silver to circulation, for the coinage was then reformed, and the establishment of the silver pound as the measure of value may be considered as the basis of all the monetary systems of modern Europe.