AT sunset on the 15th the sluice-door had been finally lowered into its place and the pent-up waters of the lake of Aeria had risen nearly forty feet by the next morning. Only the upper parts of the villas on its banks were visible and its area was so enormously increased that the whole appearance of the valley was altered.

Rising at first at the rate of three feet an hour, a rate which of course decreased as the area became greater, the waters would reach the entrance to the caverns soon after sunset on the evening of the fatal 23rd.

A little before midnight on the 21st the Orion, the sentinel ship that was on guard at the time, sank swiftly down with the news that she had made out by the light of the Fire-Cloud which, lurid and ghastly as it was, was as brilliant and penetrating as that of the sun at noonday, a large fleet of air-ships approaching from the northwards. The city was by this time almost entirely submerged. Only a few minarets and towers and the top of the great golden dome of the temple surmounted by its crystal-winged figure, showed above the surface.

The remnant of the people of Aeria, now reduced to less than seven thousand souls, including those chosen to take refuge in the caverns, were occupying the villas on the slopes of Mount Austral about the entrance to the caverns. Six thousand of them were men who had lived solely in the[351] hope of such an attack as was now about to be made and which would enable them to die fighting the common enemy of mankind to the last in defence of their beloved native land.

Not even now, when the hand of Destiny had set a definite limit to all human hopes and fears, and when the remainder of their own lives could be counted by hours, could this faithful remnant of the Aerians endure the thought that what had been their paradise and their home should be violated and polluted by the appearance of their foes.

Therefore they had lived for this last battle, and five hundred air-ships were waiting to carry them into the air to engage in the last fight that ever would be fought on earth. All their friends and kindred, saving only the Children of Deliverance, as in fond fancy they had called the little band of the chosen ones, were now dead, and the few hours of life that were left to them had nothing more to give them.

So they received with a grim joy the summons to battle which had been so long expected. Four thousand of them manned the air-ships, the rest occupied the mountain batteries, and within a quarter of an hour of the bringing of the news the war-ships had mounted into the air, and the great guns of the batteries were ready to hurl their projectiles upon the advancing foe.

It was a spectacle to make angels weep and devils laugh, this last marshalling of the forces of human hate and hostility in the closing hours of the life of humanity and on the threshold of eternity. It seemed that the Tragedy of Man was to be played out to the bitter end, and that human strife was only to cease on earth with the destruction of the world. This, too, was the work of a single woman inspired by quenchless hatred and insatiable ambition and a pride of spirit which, in its haughty incredulity, still refused to believe that the end of her conquering career had come.

Pitiless and without scruple to the end, Olga, while she was recovering from her wound under the shelter of the Sultan’s roof, had managed, with the aid of her waiting-woman Anna, not only to poison the Grand Vizier Musa and Hakem[352] the astronomer, but also to bring Khalid himself into the same state of moral slavery in which she had so long held Alan and Alexis.

It was she who had brought this fleet from Alexandria to Aeria. Once under the fatal spell of her will-poison, she had commanded Khalid to revoke the orders that he had given for peace, and he had obeyed. A fleet of more than five hundred air-ships had been collected, and, taking Khalid with her on board the Revenge, so that there should be no chance of his recovering his volition, she had come to fulfil the prophecy which Paul Romanoff uttered when in the last hour of his life he had declared that one day the Eagle of Russia should fly over the battlements of Aeria.

All the materials for constructing ten air-ships had been taken into the caverns, so that in the event of the remnant surviving the empire of the air should still be theirs, but the Alma and the Isma still lay outside the entrance when the other ships had risen into the air.

At the supreme moment a controversy had arisen as to whether or not Alan and Alexis—the latter of whom had been placed without question among the chosen, not only because of his unequalled engineering skill, but also because without him a daughter of the House of Arnold would have died of her own will—should or should not take part with their companions in the near approaching conflict.

This dispute was brought to a sudden close by Alan, who, with a sudden inspiration, cut short all the loving entreaties that were being made to him to take refuge in the caverns and avoid the chance which in the heat of the conflict might destroy with him the male line of the descendants of the first conqueror of the air.

“Do you not see,” he said, “that it is quite possible that their fleet may be twice as strong as ours, and that in spite of all our gallant forlorn hope can do they may cross the mountains and send their shells into the valley?

“What if one of them exploded here and wrecked the outworks and the entrance to the caverns? All hope, even for[353] us, would then be lost, the doors could not be lowered, and we should either have to let the waters of the lake flow out or they would flow into the caverns by the upper entrance and ruin all our labours.

“We have proved that the Alma and the Isma are the two best air-ships in existence. They can soar higher and travel faster than any others. Would it not be madness to deprive our defending force of them, and would it not be cowardice in us not to do all we can to save all that is left for us to hope for on earth? I for one shall go, and I don’t believe that I shall go alone.”

“If the Alma goes the Isma goes too,” said Alexis. “Alan is right. We should be cowards to turn our backs on the enemy at the last moment.”

“And if you go, we go,” said Alma and Isma in a breath. “If you live we will live with you, but we will not live without you.”

There was no answer to such reasoning as this, nor was there any longer any law on earth save that of individual will. The first motive power that had swayed the world was the last that survived and would be the last to die. Those of the old crews of the two air-ships who were found among the chosen at once came forward to take their places, and with them came too those who had elected to take the hazard of life or death with them.

“There shall be no widows in the new world,” said they. And so every man who rose into the air on board the two great warships carried with him the woman without whom the one last chance of life would not have been worth taking.

As they left the earth the remainder of the little company retired into the caverns, leaving two sentinels posted at the outer door ready to give the alarm in case it should be necessary to lower the doors. As they did so a long, dull, distant roar came from the northward telling that the last battle of man with man had begun.

In accordance with a plan hastily arranged before they rose, the Alma was to guard the northern end of the valley, while[354] the Isma kept watch over the southern. They soared up and up until the peaks of the mountains were a good five thousand feet below them.

From this elevation those on board the Alma could see the enemy’s fleet stretching out in a huge crescent, made up of tiny points of light which shone in the unnatural glare that illumined the earth and sky, and ever and anon they saw enormous spheres of flame blaze out along the line............