"You, nor anyone else, knew where I went when I left active service in our fleet, none but the first Air Chief, who sent me. That was a year ago, and he told me then that it was evident that the European and Asiatic Federations were preparing to attack us, and that rumors had been heard of some mighty new weapon or plan with which, if their ordinary forces failed, they would completely crush us. Hundreds of agents, said the First Air Chief, were being sent to the European and Asiatic air-cities to try to learn the nature of this new weapon, and I was one of those to be sent to Berlin, as I knew the European tongue thoroughly. I was to go in disguise, was to endeavor to work myself into the European Federation fleet, and was then to risk everything in an effort to find out what this great new plan or weapon was. And so in disguise, a year ago, I came here. "Eight months it took me to work my way into the European fleet, eight months in which I was chiefly occupied in establishing my new false identity as a European citizen. Then I enlisted in the fleet, entering the motor-section. Of course, as a cruiser-captain in our own fleet, all types of motors were perfectly familiar to me, and I had no difficulty in swiftly rising through various promotions to the status of under-officer in one of the European cruisers. Then came at last the opportunity for which I had waited for months, and which I had begun to despair of ever occurring. I was ordered to report back from my cruiser to the First Air Chief's headquarters here in Berlin, and when I did report I was questioned by a board of a half-dozen European officers on my knowledge of motors and tube-propellers. It must have seemed to them that I had unusual ability and knowledge for a mere under-officer, for they informed me that I had proved satisfactory and that I had been selected to form one of the workers on a great new work that was being carried out secretly, and ordered me to report to a certain compartment in the great air-city's base. "I reported there, eager now as I sensed myself on the trail of that which I sought, and found that there were whole vast compartments in the city's great base in which only selected men and certain high officers of the European fleet were permitted to venture. These were the compartments in which were placed the giant tube-propellers which are set horizontally in the great air-city's base, and which when the power of its great motors is turned into them move the city in any desired direction. Every air-city in the world has, as you know, these great tube-propellers that move it about. But as you know too, so much of the motors' power must be used in the life of the city, that the horizontal tube-propeller can only move the great cities through the air at an extremely slow rate of speed. It is a predicament which cannot be altered, either, by adding more motors, since to add them you must add to the city's size, and so the problem remains the same.