We had covered not more than a mile or two when we met with a new surprise. A brisk breeze began to blow over us; and the farther we walked the sharper the breeze grew, until it assumed the fury of a gale, and for the first time since reaching Atlantis I felt cold, almost as if I were back on earth. Why we continued in the face of this strange blast I could not understand, nor whence it proceeded nor how it had been produced. But while I was wondering and fighting my way through the wind, a singular whirring sound came to my ears, a buzzing as of gigantic flies; and gradually that sound grew louder, until from resembling the murmuring of insects it came to remind me of the flapping of colossal wings. That this noise was somehow connected with the quickening wind was apparent from the first; and the relationship became evident when the path swerved abruptly away from the wall and I glanced back, to behold a series of queer-looking machines supported on stone pedestals high up against the glass. It would be impossible to say just what the machines were like, for they were in such rapid motion that the parts were not visible; but there were six or eight of them, and they were round, and probably each a hundred yards across; and so swiftly were they rotating that they formed each a gray blur through which the green of the wall was vaguely discernible. “Those are the electro-intra-atomic wind generators,” explained one of the tutors. “By means of these great fans and others like them stationed at various points around the wall, the atmosphere of Atlantis is kept in constant circulation. Without them the air would be stagnant and the climate sultry and unhealthy. These generators are in action at all times, with great air-wheels that make from ten to fifteen revolutions a second; and it is estimated that the daily energy consumed by each of them would be sufficient to boil a thousand tons of ice water.” We did not linger long in the vicinity of the great fans, for the strong wind was most annoying and the temperature too low for comfort. But we set out at a brisk pace across a moss-covered plain away from the wall; and we did not pause again until we had reached the city of Lerenon, which was our destination for the day.