The sky was not overhead any longer; it was a mere strip of very dark blue, lying far off on the horizon. That is, to the right; on the left, the cavelike cleft extended still further, its limits shrouded in darkness.
"Queer, isn't it?" laughed Fort. "Shall we walk around?"
Whereupon the two young people set out on a narrow, but much worn trail. Keeping the sky always at their right, they passed through the thicket, Mona's eyes telling Billie that the queer horizontal vegetation grew always toward the light.
It was much like the growth at the bottom of any gulch; only the two were walking in the normal way, upright, at right angles to the surface, quite as though it were level ground!
Overhead the thicket grew in the same fashion; Billie thought the foliage much like ferns. Here and there, however, was a small flowering shrub; and it was to one of these that a tiny, orange-colored bird came flying.
And Billie wondered why Mona did not gasp in astonishment. For the bird, when it alighted upon the shrub, was not over eight feet above Mona's eyes; and unless there was something decidedly wrong with the girl's vision, the bird had alighted upside down!
There it clung, chirping flatly, moving its head from side to side and watching the two with bright, unfrightened eyes. But Mona was not much interested; she and Fort moved on. And shortly Billie was gazing at a fresh wonder.
Directly opposite them, on what Billie was now calling the roof, instead of the wall, there appeared a deep furrow in the ferns. She saw that it was a path, much like the one Mona was treading; it meandered in and out of sight from time to time. What was the meaning of it? Billie began to wonder if "the contact" was the name of some mechanical illusion, like a distorted mirror.
The two had been walking for nearly an hour when, right ahead of them, the thicket opened up, and another clearing presented itself. That is, Billie called it another clearing, until she looked more closely and made out two flying-machines in it. They were the ones the pair had come in!
Now Billie was positive that they had not turned around in their walk; they had kept the sky on their right all the while. In fact, the sky was still on that side. They were approaching the clearing from the side opposite the one they had gone out from!