For I saw now that that was the great barrier's nature. It was a mighty shell of perpetual vibrations in the ether itself, extending all about the universe before us, allowing light and electro-magnetic communication waves to pass through it, unchanged, but excluding and holding out the vibrations of matter, by meeting them, as I knew must be the case, with a vibration of equal frequency which opposed them, reflected them back, forming a barrier more impenetrable than any of solid matter, yet one all but invisible, extending about all this mighty universe, excluding from it for all time all matter from outside. Too, as I was later to learn, the great vibration-wall was impenetrable to the heat-vibrations, reflecting those of its dying suns that struck it back into the universe inside. It was for this purpose that the vast barrier had been erected, as the suns of the serpent-people failed, to prevent the escape of any of the precious heat-radiations of their few living suns, and also to place about all their universe a wall impenetrable to all invaders. Set in the ether about their universe eons before, the vibrations that made up the great barrier were perpetual and undying, a vast wall of defense about the serpent-universe.
We were flashing close along the mighty, flickering barrier's edge, now, and the speed of our ships slackened swiftly as there loomed far ahead in space two great, dark bulks starred here and there with points of white light. Moments more and they had grown to immense size as we neared them, and now we saw that these were mighty, square-walled structures of gleaming metal, each a full five thousand feet in length along each of its four sides, and half again that much in height: two colossal metal forts that floated motionless there in space, set directly in the great wall of flickering blue vibrations, and between which there was a great opening in that wall, a clear space in which was no flickering barrier, and which I divined was the single opening in all the great wall. And flanking that opening on either side hung the massive metal structures, upheld there in the void, as I guessed, by mighty generators like those of our own ships, castles of metal whose countless deadly death-beam tubes commanded the opening between them and from whose white-lit windows the serpent-garrisons of them gazed out upon us, great space-forts hung there at the vibration-wall's one opening, guarding the gates of a universe!
In toward the narrow opening between the great forts swept our ships, and as they moved slowly inward there flashed a challenging signal of lights from those forts, answered at once by similar signals from our ships. Then we were driving inward, between the towering metal castles on either side, flashing in through the great vibration-wall and into the dying galaxy itself. With generators again humming at high speed our half-hundred ships swept on, into the thronging thousands of dead and dying suns that swarmed before us, inside the colossal protecting shell of the great vibration-wall.
All about us now were great hordes of swarming dark-stars that we could but dimly glimpse, as our ships flashed between them, vast throngs of black and burned-out suns that outnumbered the few still flaming stars by hundreds to one. Here and there about us, though, as we swept on, we could make out a red sun or two, some comparatively brilliant and others so dark and far gone that they seemed only like giant cooling embers in the black heavens. Clusters there were, too, of which all but one or two suns would be black and dead, and as we flashed on into the depths of this universe we began to realize at last what tremendous necessity it had been that had sent the serpent-peoples driving out through the limitless void in search of a new universe.
Far ahead, though, there loomed before us as we sped on a trio of giant crimson suns more brilliant than any we had yet seen in this dying universe, and which hung at its center, each of them as large as great Canopus itself in our own galaxy. In a great triangle they hung there, two of them much brighter than the other, a mighty triplet of titanic waning suns that seemed like the dying monarchs of the vast and dying realm about them. It was down toward these three great suns that our ships were slanting now, down toward the space at the center of their great triangle, and now we saw that in that space there swung a single mighty world, a dark, immense planet of size inconceivable, almost as large as the three great suns at whose center it turned, and whose light and heat fell perpetually upon it.
Broader and broader the great turning world was growing as we slanted down toward it, until it lay like a tremendous dark shield beneath us, filling all the heavens below. As our ships sank still lower toward it, speed swiftly slackening, we began to make out details on its surface, to make out what seemed to be a vast mass of palely shining structures, towers and walls and vast, terraced buildings that glowed all with pale blue light, indescribably ghostly in appearance as they soared into the dusky, crimson light of the three encircling suns. Here and there through the masses of these blue-shining structures ran streets, narrow openings in which swarmed great masses of the writhing serpent-people. And as I gazed down upon this tremendous city, upon the countless glowing structures of pale blue light that made it up, my astonishment at what I saw broke from me in a startled cry.
"This city!" I exclaimed. "Its buildings are of vibrations like the great wall around their universe!"
A city of vibrations! A mighty city that covered apparently all this giant planet, and yet whose every structure was built, not of matter but of etheric-vibrations that were matter-resistant like the great wall, vibrations infinitely more lasting and impenetrable than any matter, and projected upward at will into buildings of any shape or size. Here and there in the mighty city, even as we sped down over it, we could see buildings vanishing instantaneously, could see other mighty buildings springing as instantly into being, all of the same pale blue light, reared or destroyed instantly by snapping on or off the vibrations that were projected upward to form them!
Now, as our ships slanted down over the vast mass of pale-glowing structures that stretched from horizon to horizon, I saw that ahead and beneath there lay amid those structures a mighty circular clearing, scores of miles in diameter and paved smoothly with the same pale blue force as the city's buildings and streets. In this vast circle, ranged regularly in long rows, rested thousands upon countless thousands of gleaming oval space-ships, in all stages of completion. Over and among them, swarming ceaselessly through them and toiling to complete them, moved mighty hordes of the serpent-creatures, armed with great tools of strange design, the thunderous clamor of their work coming up to us through the great planet's air. It was the immense workshop of the serpent-races that lay beneath us, I knew, in which their hordes labored ceaselessly to complete the mighty fleet that was to carry them through the void to our universe!