In an hour or two she reached the head of a small stream.  Hurrying down its banks as rapidly as its undergrowth would permit, Rolla followed its course as it bent, winding and twisting, in the direction which had always been north to her, but which the sun plainly labeled “south.”  Certainly the sun mounted steadily toward the zenith, passing successively through the positions corresponding to four, three and two o’clock, in a manner absolutely baffling.

About noon she came out of the canon into the foothills.  Another brief rest, and from the top of a knoll she found herself looking upon a valley about the size of the one she called “home.”  Otherwise, it was very different.  For one thing, it was far better watered; nowhere could she see the half-dried brownishness so characteristic of her own land.  The whole surface was heavily grown with all manner of vegetation; and so far as she could see it was all absolutely wild.  There was not a sign of cultivation.

Keeping to the left bank of the river, a much broader affair than any she had seen before, Rolla made her way for several miles with little difficulty.  Twice she made wide detours through the thicket, and once it was necessary to swim a short distance; the stream was too deep to wade.  The doctor watched the whole affair, purely as a matter of professional interest.

“She is a magnificent specimen physically,” he said in his impersonal way, “and she shows none of the defects of the African savages.”

And such was his manner, in speaking of his distant “patient,” that Billie took it entirely as a matter of course, without the slightest self-consciousness because of Van Emmon and Smith.

All this while Rolla had been intent, as before, upon finding some of the coveted crystals.  She had no luck; but presently she discovered something decidedly worth while—­a fallen tree trunk, not too large, and near enough to the bank to be handled without help.  A few minutes later she was floating at ease, and making decidedly better time.

A half-hour of this—­during which she caught glimpses of many animals, large and small, all of which fled precipitately—­and she rounded a sharp bend in the stream, to be confronted with a sight which must have been strange indeed to her.  Stretching across the river was—­a network of rusty wire, the remains of A reinforced concrete bridge.

There was no doubt of this.  On each bank was a large, moss-grown block of stone, which the doctor knew could be nothing else than the old abutments.  Seemingly there had been only a single span.

The woman brought the log to the shore, and examined the bridge closely.  Instinctively she felt that the structure argued a high degree of intelligence, very likely human.  A little hesitation, and then she beached her log, ascended the bank, and looked upon the bridge from above.

A narrow road met her eyes.  Once it might have been twice as wide, but now the thicket encroached until there was barely room enough, judged the doctor, for a single vehicle to pass.  Its surface was badly broken up—­apparently it had been concrete—­and grass grew in every crack.  Nevertheless, it was a bona-fide road.