This arrangement was briefly to the following effect:—Olga placed at Khalid’s disposal all the necessary plans for the construction of both air-ships and submarine vessels, and also supplied members of her own immediate retinue, well skilled in the work, to supervise the building, which was, of course, to be carried out with the utmost secrecy and speed, so as to guard, as far as practicable, against the possible destruction of the factories and dockyards by the Aerians.

The Sultan had engaged to find money and material for building a thousand air-ships, and the same number of submarine cruisers, within the year, and these were to be supplied with motive power at conversion-stations established at the dockyards under the exclusive control of certain of Olga’s lieutenants.

The secret of this motive power, which was identical save for slight differences in the process of conversion with that possessed by the Aerians—that is to say, electrical energy derived directly from atomised carbon and vaporised petroleum—was retained in her own keeping by Olga, who had simply promised that an unlimited supply of it should be forthcoming as it was wanted.

She had insisted on a strict engagement that no one not authorised by her should even approach the conversion-stations, and she had given the Sultan and his ministers distinctly to understand that any attempt to discover the secret of the process would terminate the alliance, and expose the cities of the Moslem empire to destruction.

At the expiration of the year of truce, the Sultan’s army and navy, supported by the immense aerial fleet that would then be in existence, was to be in complete readiness for any emergencies. Olga was to be proclaimed Tsarina in Moscow, and the House of Romanoff formally restored in her person. If any portions of Russia refused to receive her, they were to be terrorised into submission by the air-ships.

The tribesmen of Western and Central Asia were to be armed as rapidly as possible, so as to be ready to form a reserve force for compelling the submission of the Russians if they resisted the new order of things, and to participate in the invasion of Europe, which was to take place at several points as soon as the Holy War of Islam was proclaimed, and Cross and Crescent once more confronted each other on the battlefield.

Meanwhile, too, the resources of the dockyard at Mount Terror were to be strained to the utmost, and the conspiracy in Russia for the restoration of Olga to the throne of the Romanoffs was to be developed by every means that money could purchase or skill devise.

The scheme of defence arranged by the Council of Aeria had already been completed, and it was to execute this that the Aerian fleet had left the Russian squadron during the night. Indeed, the Russians had been travelling southward alone for more than eight hours before they had discovered the fact. As soon as it became impossible for them to see the Aerian vessels these had stopped, in accordance with a prearranged plan, and had wheeled round and steered for London across the African continent at a height of about ten thousand feet.

Flying at the full speed of the smaller vessels, a twenty-hour flight carried the fleet over the eight thousand miles which separated its starting-point from the capital of the world, and about six o’clock in the evening of the 21st of May the fifty-two vessels, flying the Aerian and British flags, appeared in the air over the open space which is now called Hyde Park, and, to the amazement of the astonished citizens, dropped quietly to the earth and lay open to the unrestricted inspection of the thousands who speedily gathered in the park to avail themselves of the unwonted spectacle, and to learn, if possible, the reason of the unexpected visit.

No attempt was made by the crews of the ships to prevent the sightseers from seeing all they could of the exteriors of the vessels, which were arranged on the sward in two long lines, so that they could walk down between them and admire their beautiful shape and wonderful construction at their leisure. A sentry was stationed by each vessel to warn the sightseers not to approach too close to the wings and propellers, and that was the only precaution taken.