the darkness beneath them, the shouts of a hurrying throng of people--an impression that might well be true since she had abundant evidence already that the cave was inhabited by a race whose number she had no means of knowing. But this reminder of the presence of others in the cave besides her own party was more disturbing to Una than the physical obstacles and dangers immediately facing her. These could at least be met and overcome--but about an invisible multitude, their attitude toward them, their purpose in apparently following them, there was an indefiniteness that was altogether disheartening. As a matter of fact, she had no doubt these hidden cavemen were hostile; her previous experiences had filled her with a vague dread in that respect. This dread, also, was sharpened by the reflection that, in all probability, Raoul was among them; of his active enmity, linked in some mysterious manner with David's disappearance, she now felt certain. Una tried to gain some light on the subject from Narva; but the latter either failed to hear the ominous sounds to which her attention was called, or she was too intent on her present mission to admit the consideration of other matters. This indifference, whether real or feigned, had a reassuring effect on Una. She perceived that if these invisible people, friendly or unfriendly, were connected with them, they would attract Narva's attention, while, if there was no connection--a conclusion suggested by the sibyl's unruffled bearing--there was nothing to fear from them. Having reached the end of the abrupt downward slope of the path they were following, Una rejoiced to find herself on the level floor of a valley that, in the upper world, would be admired for its charm and restfulness. There were neither flower-decked meadows, it is true, nor brook-fed woodland to diversify the scene. Subterranean botany, however, has its compensations for losses due to the perpetual absence of sun and rain. Evidently the light from the luminous mountain had in it some life-giving, sustaining quality, for on every hand in this valley there were luxuriant growths of delicately tinted flowers--or so they appeared--whose scent, one imagined, filled the motionless atmosphere. Tall, graceful forms, resembling willows, clustered along the banks of a little stream flowing with the gentlest of murmurs through their midst. The flinty ground was carpeted with a pale lancet-leaved herbage that might have been taken for grass were it not for the profusion of sparkling crystals with which it was sprinkled. These crystals glowed in varying and sometimes iridescent colors, showing a depth and solidity of substance decidedly out of keeping with a purely vegetable origin.