The car was now ascending; rapidly towards the pass up across the huge tumbled slopes, ravines, and cliffs that lie like outworks of the enormous wall.  Seen from this great height they were in themselves comparatively insignificant, but they at least suggested the vastness of the bastions of which they were no more than buttresses.  As Percy turned, he could see the moonless sky alight with frosty stars, and the dimness of the illumination made the scene even more impressive; but as he turned again, there was a change.  The vast air about him seemed now to be perceived through frosted glass.  The velvet blackness of the pine forests had faded to heavy grey, the pale glint of water and ice seen and gone again in a moment, the monstrous nakedness of rock spires and slopes, rising towards him and sliding away again beneath with a crawling motion—­all these had lost their distinctness of outline, and were veiled in invisible white.  As he looked yet higher to right and left the sight became terrifying, for the giant walls of rock rushing towards him, the huge grotesque shapes towering on all sides, ran upward into a curtain of cloud visible only from the dancing radiance thrown upon it by the brilliantly lighted car.  Even as he looked, two straight fingers of splendour, resembling horns, shot out, as the bow searchlights were turned on; and the car itself, already travelling at half-speed, dropped to quarter-speed, and began to sway softly from side to side as the huge air-planes beat the mist through which they moved, and the antennae of light pierced it.  Still up they went, and on—­yet swift enough to let Percy see one great pinnacle rear itself, elongate, sink down into a cruel needle, and vanish into nothingness a thousand feet below.  The motion grew yet more nauseous, as the car moved up at a sharp angle preserving its level, simultaneously rising, advancing and swaying.  Once, hoarse and sonorous, an unfrozen torrent roared like a beast, it seemed within twenty yards, and was dumb again on the instant.  Now, too, the horns began to cry, long, lamentable hootings, ringing sadly in that echoing desolation like the wail of wandering souls; and as Percy, awed beyond feeling, wiped the gathering moisture from the glass, and stared again, it appeared as if he floated now, motionless except for the slight rocking beneath his feet, in a world of whiteness, as remote from earth as from heaven, poised in hopeless infinite space, blind, alone, frozen, lost in a white hell of desolation.

Once, as he stared, a huge whiteness moved towards him through the veil, slid slowly sideways and down, disclosing, as the car veered, a gigantic slope smooth as oil, with one cluster of black rock cutting it like the fingers of a man’s hand groping from a mountainous wave.

Then, as once more the car cried aloud like a lost sheep, there answered it, it seemed scarcely ten yards away, first one windy scream of dismay, another and another; a clang of bells, a chorus broke out; and the air was full of the beating of wings.