"Radio-active," he commented. "All this glowing rock and soil." Then he straightened, glanced around, and led the way unhesitatingly through the thicket of black forest into which our ship had fallen.

Silently we followed him. in single file, across the shining soil and beneath the distorted arches of the twisted trees, until at last we emerged from the thicket and found ourselves upon the open expanse of the glowing plain. It was a weird landscape which met our eyes, a landscape of glowing plains and shallow valleys patched here and there with the sprawling thickets of black forest, a pale, luminous world whose faint light beat feebly upward into the dusky, twilight skies above. In the distance, perhaps two miles ahead, a glow of deeper light flung up against the hovering dusk from the massed buildings of the luminous city, and toward this we tramped steadily onward, over the shining plains and gullies and once over a swift little brook whose waters glowed as they raced like torrents of rushing light. Within an hour we had drawn to within a distance of five hundred feet from the outermost of the city's pyramidal buildings, and crouched in a little clump of dark tree-growths, gazing fascinatedly toward it.

The scene before us was one of unequaled interest and activity. Over the masses of huge, shining buildings were flitting great swarms of the long black cones, moving from roof to roof, while in the shining streets below them moved other hordes of active figures, the people of the city. And as our eyes took in these latter I think that we all felt something of horror, in spite of all the alien forms which we were familiar with in the thronging worlds of the Galaxy. For in these creatures was no single point of resemblance to anything human, nothing which the appalled intelligence could seize upon as familiar. Imagine an upright cone of black flesh, several feet in diameter and three or more in height, supported by a dozen or more smooth long tentacles which branched from its lower end-supple, boneless octopus-arms which held the cone-body upright and which served both as arms and legs. And near the top of that cone trunk were the only features, the twin tiny orifices which were the ears and a single round and red-rimmed white eye, set between them. Thus were these beings in appearance, black tentacle-creatures, moving in unending swirling throngs through streets and squares and buildings of their glowing city.

Helplessly we stared upon them, from our place of concealment. To venture into sight, I knew, would be to court swift death. I turned to Hurus Hol, then started as there came from the city ahead a low, waxing sound-note, a deep, powerful tone of immense volume which sounded out over the city like the blast of a deep-pitched horn. Another note joined it, and another, until it seemed that a score of mighty horns were calling across the city, and then they died away. But as we looked now we saw that the shining streets were emptying, suddenly, that the moving swarms of black tentacle-creatures were passing into the pyramidal buildings, that the cones above were slanting down toward the roofs and coming to rest. Within a space of minutes the streets seemed entirely empty and deserted, and the only sign of activity over all the city was the hovering of a few cones that still moved restlessly above it. Astounded, we watched, and then the explanation came suddenly to me.

"It's their sleep-period!" I cried. "Their night! These things must rest, must sleep, like any living thing, and as there's no night on this glowing world those horn-notes must signal the beginning of their sleep-period."

Hurus Hol was on his feet, his eyes suddenly kindling. "It's a chance in a thousand to get inside the city!" he exclaimed.

The next moment we were out of the shelter of our concealing trees and were racing across the stretch of ground which separated us from the city. And five minutes later we were standing in the empty, glowing streets, hugging closely the mighty sloping walls of the huge buildings along it.

At once Hurus Hol led the way directly down the street toward the heart of the city, and as we hastened on beside him he answered to my question, "We must get to the city's center. There's something there which I glimpsed from our ship, and if it's what I think-"

He had broken into a run, now, and as we raced together down the bare length of the great, shining avenue, I, for one, had an unreassuring presentiment of what would happen should the huge buildings around us disgorge their occupants before we could get out of the city. Then Hurus Hol had suddenly stopped short, and at a motion from him we shrank swiftly behind the corner of a pyramid's slanting walls. Across the street ahead of us were passing a half-dozen of the tentacle-creatures, gliding smoothly toward the open door of one of the great pyramids. A moment we crouched, holding our breath, and then the things had passed inside the building and the door had slid shut behind them. At once we leapt out and hastened on.

We were approaching the heart of the city, I judged, and ahead the broad, shining street we followed seemed to end in a great open space of some sort. As we sped toward it, between the towering luminous lines of buildings, a faint droning sound came to our ears from ahead, waxing louder as we hastened on. The clear space ahead was looming larger, nearer, now, and then as we raced past the last great building on the street's length we burst suddenly into view of the opening ahead and stopped, staring dumfoundedly toward it.