This aerial review was the concluding spectacle of the festivities, and it was watched by the occupants of thousands of pleasure-craft, whose interest in it was sharpened by the knowledge that before many days a conflict such as it portrayed might be raging in deadly earnest round the mountain bulwarks of their hitherto inviolate domain. So consummate was the skill displayed by Alan in this defence that as soon as the _Avenger_ touched ground after the review was over he was summoned to the Council Chamber in the President’s palace to receive the thanks of the Senate and cordial expression of the perfect confidence that the people of Aeria would feel, whatever the magnitude of the war might prove to be, while the conduct of the campaign was in his hands and those of Alexis, whose tactics had also been so perfect that, without once putting a single ship in danger, he had made it impossible for Alan to do anything more than remain strictly on the defensive. On the following day, the 14th, the motive power of all the vessels was renewed, ammunition laid in, and all the guns and engines minutely inspected, so that there might be no chance of failure when the moment of trial came. Then the final arrangements for the defence of Aeria itself were perfected, and when that was done, the Vale of Paradise, as its inhabitants fondly called their lovely land, was a vast fortress compared with which the strongholds of the present day would be as harmless and defenceless as molehills. Four hundred aerial battleships of what were now called the first and second classes, ranging in speed from four to five hundred and fifty miles an hour and mounting from ten to twenty guns each, were to patrol the outer walls of the mountains, at distances of five and ten miles from them and at elevations varying from two to ten thousand feet. These were divided into two fleets of two hundred each which relieved each other every six hours, so that their supply of motive power might be constantly renewed. In addition to these, two squadrons of twenty-five of the most powerful warships of the newest type alternately kept watch and ward against surprise in the upper regions of the air from fifteen to twenty thousand feet above the valley, while all round the great circuit of the mountains were planted in the most favourable positions nearly a thousand land batteries mounting three, five, and ten guns each, which, if necessary, would be able to surround Aeria with a zone of storm and flame which nothing living could pass and still live. [Illustration: BATTERIES WHICH WOULD BE ABLE TO SURROUND AERIA WITH A ZONE OF STORM AND FLAME. _Page 248._] By day the range of vision from the decks of the sentinel ships would make surprise impossible, and at night the great electric suns on the summits of the mountains, aided by hundreds of search-lights flashing through the darkness in every direction, made an attack under cover of the darkness almost equally hopeless.