Before I had had time to reply, fresh alarm swept aver us both; once more the earth wavered violently and the distant thunders and detonations burst out with renewed fury. At the same time, a shaft of violet light, from some unknown source, shot across the cavern with lightning swiftness. Then, in the barest fraction of a second, waves of orange light and of vermilion followed; then, while Clay and I stared at each other in consternation, the greenish-yellow luminaries all flickered and seemed about to be extinguished. Simultaneously, our ears were struck by a distant blast of sound, a little like the notes of a bugle; and the next instant, as the greenish-yellow lights regained their former brilliancy, a scene of startling activity became visible on the cavern floor.
Had we obeyed the dictates of our hammering hearts, we should have turned and fled. The impulse to flee was, indeed, powerful within us; but partly because we did not wish to seem cowards in each other's eyes, and partly because of our insatiable curiosity, we fought down our self-protective instinct, flung ourselves full-length upon the gallery floor, crept to the edge of the abyss, and gazed across. And there, in that recumbent position, like small boys secretly watching a ball game, we witnessed a spectacle so unimaginably strange that I cannot recall it even today without a shudder of the old horror.
CHAPTER IV
Thunderbolts
From our vantage-point near the cavern roof, we could not clearly follow all that was happening a mile beneath; however, we were able to observe more than a little. In the beginning, we were astonished to see the doors at the base of the excavation all thrown open, to admit a multitude of black ant-like mites, which we did not at first recognize as human beings. So minute were they, in view of their distance, that they might have been mere swarming insects. To discover much about their appearance or costume was out of the question; nevertheless, we were not long in learning their nature, for they immediately drew themselves up into precise rectangular formations, each of which was divided into scores of long, mathematically even columns.
"By Heaven!" I gasped, as I lay peeping across the edge of the abyss. "If it isn't an army!"
"Sure enough, an army!" agreed Clay, his mouth agape till the lower jaw seemed ready to drop off. "I'll swear they look like the devil's own recruits! Just see the banners gleaming!"
By straining my eyes, I could distinguish flashes of yellow and purple, as from the waving of battle flags.
"Say, look down there!" my companion ejaculated the next second, leaning over the edge of the void until I feared he would take a mile-long fall. "There's not one army! There's two!"