A fearful scene unfolded itself before them as they swept up out of the eastward over Paris. The vast and splendid city was surrounded by a huge circle formed of at least two hundred Moslem warships floating at an elevation of some three miles, and pouring a tempest of projectiles from hundreds of guns indiscriminately into the area crowded with stately buildings and nearly ten millions of inhabitants. [Illustration: A FEARFUL SCENE UNFOLDED ITSELF AS THEY SWEPT UP OVER PARIS. _Page 286._] Nearly three miles above the centre of the city floated a solitary scout-ship ready to signal warning of the approach of an enemy. Fires were already raging in hundreds of places all over the city. The streets were swarming with terrified throngs of citizens who had rushed out to escape the flames and the falling buildings, only to meet the hundreds of shells that were constantly bursting among them, rending their bodies to fragments by scores at a time. Such was the beginning of Khalid the Magnificent’s revenge for the disaster of the Mediterranean--a vengeance which proved that, in his breast at least, the savage spirit of the ancient warfare was still untamed. The _Avenger_ and the _Isma_ gained an altitude of four miles above the doomed city, half a dozen shells from their guns struck the scout-ship and reduced her to dust before she had time to make a signal in warning, and then the forty-four guns began to send a radiating hail of projectiles upon the Moslem fleet. Shell after shell found its mark in spite of the vast range, and ship after ship collapsed and dropped in fragments or blew up like a huge shell. But before the fifth round had been fired a strange thing happened. A single Aerian warship rushed up at full speed out of the south, and as soon as she sighted the _Avenger_ signalled, “Orders from the Council. Come alongside.” The new-comer soared upwards as they sank to meet her, and the three ships met and stopped some three miles and a half above the earth. The stern of the _Azrael_, as the messenger-ship was named, was brought close up to that of the _Avenger_, the deck doors were opened, a gangway thrown across, and the captain boarded the flagship and placed a sealed despatch in Alan’s hand. He opened it, and to his unspeakable astonishment read-- AERIA, May 16th, 6 P.M. All Aerians are to return at once with their ships to Aeria, and take no further part in the fighting. The Federation fleets may be left in the hands of foreign crews and commanders, to whom the power-stations and batteries are to be given up. This order is to be obeyed with the least possible delay. ALAN ARNOLD, President. To the Admirals in command of the Federation Fleets. CHAPTER XXV. A MESSAGE FROM MARS. IN order to adequately explain the origin of the peremptory recall which, although of course he obeyed it without question, seemed so incomprehensible to Alan, it will be necessary to go back to the night of the 12th of May.