"But now, as I found when I first entered those compartments, these European Federation officers and inventors had solved that problem! They had devised a way that would enable them to send their gigantic air-cities rushing through the air at almost the speed of a cruiser itself! They had done this by devising a wholly new form of horizontal tube-propeller capable of infinitely greater tractive effect on the air and rotating at a much higher rate of speed. Thus the great air cities, miles across and with all their towers upon them, could rush through the air at hundreds of miles an hour, needing only to use their vertical tubes when they were hovering motionless in mid-air or were moving very slowly. "And _this_ was the great weapon, the great plan, of the European and Asiatic Federations! For I saw at once that it was a great weapon indeed, a terrific weapon which would enable them to annihilate all the air-cities and peoples of our own nation. You see what it meant? It meant that they could gather together all their scores of giant air-cities, outnumbering our own one hundred cities by two to one, and could rush over the oceans at awful speed toward our American air-cities, could fall upon them with all the giant batteries of heat-guns with which each colossal city is equipped, like our own. And because our own would not be able to move at that tremendous speed, because our own air-cities could only move at a comparatively creeping rate through the air, they would be able to mass their outnumbering forces around our own cities and blast them from the air, annihilating them and all the millions of our people inside them, sending them hurtling to earth in titanic fusing wrecks!