The restless Ralph, who had chafed a good deal because he had not been allowed to leave the plateau in search of adventure, now found a vent for his surplus energy, for the captain appointed him fire-maker.  The camp fuel was not abundant, consisting of nothing but some dead branches and twigs from the few bushes in the neighborhood.  These Ralph collected with great energy, and Maka had nothing to complain of in regard to fuel for his cooking.

Toward the end of that afternoon, Ralph prepared to make a fire for the supper, and he determined to change the position of the fireplace and bring it nearer the rocks, where he thought it would burn better.  It did burn better—­so well, indeed, that some of the dry leaves of the vines that there covered the face of the rocks took fire.  Ralph watched with interest the dry leaves blaze and the green ones splutter, and then he thought it would be a pity to scorch those vines, which were among the few green things about them, and he tried to put out the fire.  But this he could not do, and, when he called Maka, the negro was not able to help him.  The fire had worked its way back of the green vines, and seemed to have found good fuel, for it was soon crackling away at a great rate, attracting the rest of the party.

“Can’t we put it out?” cried Miss Markham.  “It is a pity to ruin those beautiful vines.”

The captain smiled and shook his head.  “We cannot waste our valuable water on that conflagration,” said he.  “There is probably a great mass of dead vines behind the green outside.  How it crackles and roars!  That dead stuff must be several feet thick.  All we can do is to let it burn.  It cannot hurt us.  It cannot reach your tent, for there are no vines over there.”

The fire continued to roar and blaze, and to leap up the face of the rock.

“It is wonderful,” said Mrs. Cliff, “to think how those vines must have been growing and dying, and new ones growing and dying, year after year, nobody knows how many ages.”

“What is most wonderful to me,” said the captain, “is that the vines ever grew there at all, or that these bushes should be here.  Nothing can grow in this region, unless it is watered by a stream from the mountains, and there is no stream here.”

Miss Markham was about to offer a supposition to the effect that perhaps the precipitous wall of rock which surrounded the little plateau, and shielded it from the eastern sun, might have had a good effect upon the vegetation, when suddenly Ralph, who had a ship’s biscuit on the end of a sharp stick, and was toasting it in the embers of a portion of the burnt vines, sprang back with a shout.

“Look out!” he cried.  “The whole thing’s coming down!” And, sure enough, in a moment a large portion of the vines, which had been clinging to the rock, fell upon the ground in a burning mass.  A cloud of smoke and dust arose, and when it had cleared away the captain and his party saw upon the perpendicular side of the rock, which was now revealed to them as if a veil had been torn away from in front of it, an enormous face cut out of the solid stone.