THE BYZANTINES. 87 could develop against attacks, and what great ad- vantages its site offered in keeping together a reign extending into three continents. Con- stantinople during the time of the Byzantines until the days of terror of the Prankish conquest in 1204 was a marvellously beautiful city and at the same time the most powerful military strong- hold of the whole Middle Ages. Against the attacks of all the hordes which the Byzantines had to fight before the year 1204 the city was almost invulnerable, especially since they had in the Greek sea fire a weapon of most terrific effect. This fire was the inven- tion of a Greek, Kallinikos of Heliopolis. It consisted of a mixture of combustibles, contain- ing naphtha, sulphur, pitch, and other ingre- dients, which burned even under water. When the incendiary ships with their copper cylinders containing the composition for the destructive fire came near to the battle-ships of the enemy the latter was overtaken by fright and fear. The formula of the composition was kept a state secret. The Byzantines were enabled repeat- edly to destroy large masses of enemies under the walls of their capital, and thus to save an empire which otherwise would have been lost. The imperial government has been accused
