Khalid looked down at the city, over which they were now speeding in the direction of Medinah, and was silent for a few moments; then he raised his eyes to hers and said-- “Even so; but have you counted the cost of achieving it to me and my people? Before the banner of the Crescent could float over a world-wide empire of Islam we should have to triumph in a war which would involve the whole human race, and this means that we should first have to destroy those who have been lords of the earth and of the air for more than a century.” “The Aerians are but men,” said Olga, a trifle coldly. “Why should your Majesty fear them if you are armed with the same weapons that they wield? I suppose Alan Arnold has threatened you and your people with nothing less than annihilation should you conclude this alliance with me? But why should you fear? I have met the Aerians in battle, and you see I am not annihilated.” “I do not fear them as personal enemies,” replied Khalid proudly, “but only as the possible destroyers of my people, who would be defenceless against them. Think of the destruction you could rain upon the sacred city down yonder, while it could strike no blow in return. That would be the fate of Alexandria and all the capitals of my empire, and while my armies were marching to the conquest of Christendom our homes would be laid in ruins and our wives and children slain without mercy. “Show me,” he continued, speaking more earnestly and rapidly, “how they are to be protected against this, and our alliance may become possible.” “It is purely a matter of relative strength,” replied Olga. “Do you know why this squadron of mine is allowed to pursue its way unmolested, although the Aerians know of its existence? It is because, although, as Alan Arnold truly told you, by superior skill and experience in handling their ships they have been able to destroy about half my fleet, I am still stronger in the air than they are, and they know that we have now gained the experience which we lacked. “They have only three vessels, counting the one you saw captured, as swift and powerful as this, while I have twenty-six. None of their smaller vessels dare venture within reach of my guns, for to do so would be to meet certain destruction. They are doubtless building others as strong and swift as these in preparation for the struggle which they know must come. But if we join hands against them we shall be stronger than they will be when the year of your truce is ended. “My engineers shall teach yours how to build air-ships in all respects equal to these, and submarine cruisers, a dozen of which could destroy your present navies in a day. With all the resources of your empire at command, you could possess in a year from now an aerial navy of a thousand ships and a sea fleet of equal strength.