The gateway to the depths was that which appeared to be a photographer's dark-room. Once inside, Mallory pressed certain carved ornaments, the entire farther wall slid back, and there stretched before us a smooth, well-lighted passage leading downward at a gentle incline.
We must have followed this more than a half mile before we debouched into the main cavern; a mighty, vaulted chamber, a huge bubble of emptiness blown in the solid mountain centuries ago when Earth was in the travail of making.
But it was not this natural wonder that made me gasp. I had seen others; I had, indeed, once taken refuge for four weeks with the Ninth Artillery in Luray. That which brought an exclamation to my lips was the shimmering monster braced on an exoskeleton of girders in the middle of the chamber. A g
