The travelers were up among the hills by now. Occasionally they passed a deserted cabin, home of some early gold-digger. Valleys dark with night opened up to right and to left as the Forty Mile wound higher, deeper into the maze of rounded domes: the Boundary was close at hand. The hillsides hid their feet in black thickets of spruce, but their slopes were thinly timbered, their crests were nearly bare, and the white snow gave off a dim radiance that made traveling possible even after the twilight had deepened. By and by it grew lighter and the north horizon took on a rosy flush that spread into a tremendous flare. The night was still, clear, crackly; it was surcharged with some static force, and so calm was the air, so deathlike the hush, that the empty valley rang like a bell. That mysterious illumination in the north grew more and more impressive; great ribbons, long pathways of quivering light, unrolled themselves and streamed across the sky; they flamed and flickered, they writhed and melted, disappearing, reappearing, rising, falling. It was as if the lid had been lifted from some stupendous caldron and the heavens reflected the radiance from its white-hot contents. Mighty fingers, like the beams of polar search-lights, groped through the voids overhead; tumbling waves of color rushed up and dashed themselves away into space; the whole arch of the night was lit as from a world in flames. Red, yellow, orange, violet, ultra-violet--the tints merged with one another bewilderingly and the snows threw back their flicker until coarse print would have been readable. Against that war of clashing colors the mountain-crests stood out in silhouette and the fringe of lonely wind-twisted trunks high up on their saddles were etched in blackest ink. It was a weird, an unearthly effect; it was exciting, too. As always when the Aurora is in full play, the onlookers marveled that such a tremendous exhibition of energy could continue in such silence. That was the oddest, the most impressive feature of all, for the crash of avalanches, the rumble of thunder, the diapason of a hundred Niagaras, should have accompanied such appalling phenomena. It seemed odd indeed that the whine of sled runners, the scuff of moccasins, the panting of dogs, should be the only audible sounds.