All the sentinel ships had now been withdrawn save one, which, from a height of fifteen thousand feet, still kept watch and ward against the coming of the foe that was even yet expected. But this was the only sign of life within the confines of Aeria, and when the solemn ceremony was ended and the assembly filed out of the doors, the members of it betook themselves almost in silence to their homes, there to make their final preparations for life or death as Destiny had selected them to live or die. CHAPTER XXXI. THE LAST BATTLE. 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 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.